I don't know why I'm feeling like this?!?

I actually don't know what I'm doing or thinking any more, things are getting too much and I'm not sure how to cope with any of it. This is a bit long, and maybe complicated, so I'm sorry and thank you for taking the time to read it.

Well I have been with my current boyfriend for 10 months not and things have been amazing. He has a bad history of cheating on his girlfriends so I was a bit unsure about been with him but he has never gave me reason to not trust him. He has also got two kids with his ex which some times gets to me because he is still talking to her and I think that he is going to go back to her because she has his kids and he was sleeping with her when he was with his most recent ex.

Anyway I am sick of feeling like I do. I am always thinking the worst of everything, I always think he is cheating on me and stuff like that. It's not really bad to the point where I am always accusing him but when I do tell him how I feel he always just tells me that there is nothing to worry about, and he never kicks off about it what so ever. I love him I really do and I am sick of feeling like this because it will end up coming between us in the end and it will be my fault. I just don't know how to stop these feelings.

The main thing now though is that a few weeks ago I found out I was pregnant and we wern't sure what we wanted to do with it, as I am in university and he already has two really young kids and we haven't been together that long. But anyway I went to the hospital to check how far I was and to talk to someone about it. When I got the scan I got told that it had no heart beat at all, and at this point I was sure that I wanted to keep it because I would regret it otherwise. So I was pretty gutted about this because I could not keep it anyway. I told my boyfriend and he has been there for me all the way through it, he hasn't talked about it much but if I have needed him he has been there. The thing that is hurting me is that it might not have been so bad for him because he already has kids and it just scares me that he will now go back to his ex.

I know this is all stupid and it's me just been insecure about things that I shouldn't be but I really can't help it. I try to keep myself busy when I get these thoughts but nothing I do seems to help me and I don't want to lose the love of my life because I'm been stupid.

Just any advice would be helpful.

Thank you all in advance.

Sarah x x