Am I wrong for doing this?

I guess this is a little personal but me and my baby's father had broke up but now we are back together. I'm still pregnant and he's been wanting to have sex. I know he's been with someone else while he wasn't with me and I'm just nervous about any possible std's being transferred from that other woman cause he was clean while he was with me so I had no worries then. I mentioned to use condoms but he insists that he's clean. I don't want to upset him by saying no but I'm just trying to look out for our baby's health. I just have to learn how to say no. No glove, no love!