After some advice

So Ive been having suspicions that my husband was having an affair. Little thing just weren’t adding up for me, we had had sex for ages air any sexual interaction for that matter but that was mainly my fault due to having an 8 month old baby and being tired all the time and also having the implant which didn’t help, anyways a things I had noticed such as : went to my parents but he didn’t want to go he wanted to stay home, he had started taking my kids out on play dates more, he also kept meeting up with his “mate” but never told me their name., he also take his phone with him everywhere. Then 2 weeks before xmas I saw a message pop up on his phone( he’d actually left it to go to the toilet) from a girl. So I checked his Facebook the next day while he was at work, I know I shouldn’t but I couldn’t help myself. I found nothing! So I messaged him to say I had checked his Facebook and asked him if he was seeing anyone else behind my back. He said no he explained everything saying he didn’t tell me his friend is a woman from work she has helped him with his anxiety as she has been dealing with it as well. He said nothing has happened with her they were just friends. So I let him come come and we agreed to put it behind us and try again for the kids sake. But I just can’t get it out of my head and keep thinking of Little’s things that don’t add up. Like the weekend I went to my parent he decided to change the bedding randomly which he never does. He said he was going to the gym one night last week but it was only open 10-2 but he went at 7-9 and said that it’s open the same time this week but when I’ve asked in a Facebook group everyone has said it’s only open 10-2. She has also blocked my on Facebook now. I really want to believe him but things just don’t add up, he’s now back at work and I’m worried he’s gunna be spending time with her. What should I do? Would you believe him? X