cheating

ok so I have been with my so for 4 years and 9 months ago he cheated on me wit hb a ex it was not the first time with the same persona but the last time I left for a few days. week are great together and he has cut all ties with her has her blocked on everything. but the thing is I'm prego and at the time he cheated I was so me being pregnant has been a big trigger and I have for gave him and we have worked it out but . ever seems I found out I was pregnant I keep thinking what if it happens again . it makes me sick at times I love this man more then anything and we have been very happy but I tend to get in my feelings and I dont know what to do from having that thought s and the far. please help