Help! I took a shower and noticed strong oder and my boyfriend thinks its because im cheating!?

Hi, I don't know if this info will help, but a little about myself is i am 17 and 3 months pregnant. I recently was sick (lots of throwing up, extrem stomach pain, and constipation.) but feel a little better, besides being a little nausus. And also around friday my boyfriend and i kinda had rough and my uterus hurt a little bit the next day and i thought i had a urinary tract infection, but the pain went away, but like i said i don't know if any of this could be a factor haha. Well last night (monday) my boyfriend and i had a date planned for 6pm, so i took a shower at 5pm. I thought i was goin to be late, so i put on my pants (which id been wearing all day and god knows how long ago i washed them, i know its gross) with no undies because i couldnt find a nice pair and figured we'd be havin anyway and didnt need them. My boyfriend didnt end up coming tell about 8 and we went out to eat. I then went to the bathroom and then we were off to do our business. When we started getting intimate, I was already very wet from bein . I took off my pants and noticed a strong oder, but thought it was just from being . I then got a whiff of it and so did my boyfriend and then i got so eembarred It smelt kinda fishy and like i hadnt washed in days but i just took a shower not even 3 hours ago! My boyfriend started acting weird and i was hopen hed understand that a girls smell isnt always pleasant. But now he thinks its because i cheated on him!!!! Yea i was really wet, but that always happens. I just dont know about the smell part! I dont know if its from not wearing undies with my dirty pants, or if i didnt wipe well in the bathroom, or something more serious. Im scared it might be something bad up there and could end up harming the baby. And its affecting my relationship. I love my boyfriend to death, but he knows nothing about a womens body and health!!! He umes if im not my "normal" smell and wetness im cheating!!! It's not fair! Can someone please tell me what could be wwrongand post some sites so my boyfriend can believe me!! I cant help what my body dose!!!