Cheating or just companionship?

My husband talks non stop about his coworker. Like if she was his best friend. Theyre always together. But thats kind of his job. They work together on projects for the company and its only 4 of them in the dept. The other two either dont live in this state or hes kind of the boss so he doesnt deal as much 1 on 1 with the team. Anyway...non stop talk about her. He recently got on this crazy diet. Hes always wanted to lose weight but he never follows through. All of a sudden hes super determined and seems to be getting motivated by her because she tries hard to eat healthy. Apparently she signed up for some marathon and out of nowhere my husband joined too. Its not a work thing but he did the most and asked his company to sponser them basically. Anything that has to do with gays he could care less. We have different point of veiws on the matter but over all he says its not for him and he doesnt want anyone pushing that on our kids. Fine whatever. Tell me why today he decided to go to a pride parade with non other than his coworker to "support" his boss because he just came out as gay. He asked if i wanted to go but he knew i could. Who going to take care of the kids? He just seems to just really enjoy her company and idk what to do or think. Ive told him before how much it bothered he always talked about her. Maybe im over exaggerating? Maybe im over thinking things because i dont get to just leave the house when i feel like it? I just became a SAHM. 30 weeks pregnant. A 4, 9,10, 11 yr old at home. Two who are his kids with his ex but i raised because she left long time ago. 1 with my ex. One of his kids is autistic and im the only whos ever dealt with it. I just feel used and not appreciated. And he would rather spend time somewhere else? Excuse my rant...i think i just wanted to get it out there like if i actually talked to someone about it. .