How likely does a husband cheat within 1st year of marriage, expecially with MUCH older woman?

Been married for almost 9 months and I am 8 1/2 months preggo. We have had an awesome realtionship but things have been rocky since I been preggo cuz I been so sick and moody. We have fought more since I been preggo than ever!!! We love each other very much. Since I been preggo I have been VERY insecure and have made comments about co-workers of his and I have been watching him like a hawk when he steps out the door. I am freakin out since tomorrow they both have the day off. I am thinking of setting up my voice recorder or camera when i leave. I am turning into a crazy person! I know he wouldnt do anything to hurt me but I cant help but wonder! He lied to me about how old she was. What else has he lied to me about? We live in the same apartment complex I have met her. She is "married to another woman" but has a kid so she has been with men before. He has never given me any signs to think he has done anything! Why am I acting like this??? She is like 15 yrs older than him anyway!!!! I pray to God its just the hormones!!!! I have never freaked out this bad!!! One thing that I have noticed is when she is around he looks at her alot! I dont know!!!!!