my hubby is convinced I'm cheating

So apparently because I'm on my phone a lot, it means I'm cheating. We have a four month old daughter and have been married for a year, together for six. I admit I am on my phone a lot but I like to read. My baby is breastfed so that's really the only thing I can do when she's nursing. I read Facebook, mommy forums, baby forums and watch YouTube. I'm not talking to anyone sexually I would never. He also thinks it's with a guy that's in my contacts. The guy is a gay coworker and Facebook automatically synced it to my phone