Therapist A is a counsellor with a psychodynamic approach with experience of working with adults and young people.

You are asking for help to change. You would like to develop a genuine respect for yourself so that you could believe that you are loveable and not feel the pangs of jealous doubt. I think you are suggesting that it is difficult for you to be close to someone without feeling that you may be betrayed by them. Your pregnancy may be intensifying the difficult feelings you are having. The idea of the responsibility you will have to the baby and the fact that you are going to feel even more dependent on your partner may be intensifying your feelings.

You say that you donít have any bad experience in previous adult relationships but I wonder about how things might have been in your family. You donít give any clues as to what your relationships with parents and siblings were like. Feelings of insecurity and jealousy often do come from when we were very little but donít emerge until we get into a close relationship or sexual partnership.

It is good that you recognise how damaging your jealousy of your partnerís past relationships and your fear of being betrayed are to what you have between you. It may be quite difficult for him to understand why you get so accusatory.

Without knowing a lot more it is difficult to be very helpful. I do think it would be good to find a counsellor to talk things through with, as, in order to change, you need to understand the roots of your jealousy and insecurity. These feelings can take a while to work through. Meanwhile, try to catch yourself before you start accusing your partner and perhaps tell him what you are feeling. Also try to put yourself in his shoes and imagine what it feels like to be him when you accuse him.

Therapist B is a Relate-trained counsellor with experience of working with relationship issues and is an experienced couples counsellor

I'm sorry to read about you thinking that you "just do not love & respect myself enough to believe that others can love me", & interested that you can't make any connections from past events that might have contributed to what sounds like low self esteem? I'm sending a link to a site which could be useful for you to read & realise that many people, men & women, have a similar problem, leading to a lack of self confidence in themselves.
There are many more sites on the same theme on Google but this one (below) has a very sensible approach, & gives some simple exercises to try & help you make some changes in your attitude, particularly as you are now pregnant & may be feeling even more vulnerable.
You explain that the pregnancy has changed your feelings towards your partner & made you question his loyalty, although it sounds as though he is being as supportive as he can. I wonder if it would help you to try & explain how these feelings of insecurity are affecting your confidence in this new situation,& ask him how he too is feeling generally? Sometimes it is easier to stay with how you are feeling to the exclusion of sharing your thoughts & fears with each other.
I think you'll find that reading through the information on the site(s) below first might help to clarify what is worrying you the most,& help you to find a quiet time to talk to your partner about how this forthcoming change in the relationship is affecting you.
If couples can communicate as honestly as possible then it can help to discover more about your partner, but I do understand that sometimes saying your concerns aloud can be a bit daunting if you're not used to revealing your inner thoughts to anyone. However, this is the father of your baby & you have now shared your worries here online, so I hope it will help you to take the next step of finding out more about yourself, & taking him into your confidence bit by bit.
I know it is hard to adjust to pregnancy at any stage of your life,& quite often men feel left out & helpless, but this could be an opportunity for you to start to trust him bit by bit by asking for specific help & support in planning your Dr appointments etc,& talking about your hopes & fears for the future?
I hope the sites help you to feel less alone, & that you will feel free to come back & discuss anything that is still troubling you. There are other ways of getting therapeutic support online which can be found on google but I hope that these will help get you started & provide you with the knowledge that there is help available.

Therapist C is a psychoanalytic psychotherapist with experience of working with relationship and many other issues.

I wonder where the fear of something bad happening comes from. There is a British psychoanalyst called Winnicott who wrote that the worst has already happened and our fear of the worst happening is due to our fear of what has happened happening again. You seem to be trying to find reasons which would explain why your partner would want to leave you. It is almost as though you are preparing for the worst, which does not seem likely this will happen, from you say about your partner. I wonder what has contributed to your feeling unlovable and expecting to be hurt. You do not say anything about your childhood or your relationship with your parents. Did they give you the feeling that you were loved and valued for who you are or they did give you the feeling that you were unlovable? It is likely that the pregnancy is intensifying your feelings of vulnerability and your fear of abandonment. It might be worthwhile for you to have some sessions with a counsellor or psychotherapist to help you to understand the origin of these frightening feelings so that you can work through them.