Did he cheat? Has he? will he?

Idk if its my hormones or wth. But I had my baby shower last week my SO's co worker came I noticed that every time she will go the restroom he will dissappear. A couple times after, we were greeting guests and she came to him and asked if she can use the restroom, he said yes. Couple seconds later he said "u know what I'll go with you I gottah go get something from the house" they both did take a while to come back. Or maybe i didnt notice them comeback? they were both drinking so that got me a little nervous when he said he will go with her...Idk I'm going crazy thinking about it. Will he actually do it? I honestly don't know :/...we been together for 4 years. And it will suck to know if he did something with her. By the way I met her last year at he's work christmas party and she seemed a little too playful....I've never been the jealous type till now. And it's driving me insane