Huge relationship problems need advice

About 2 years ago I found out my boyfriend was using an online sex chat. He said it was anonymous and that he didn't know anyone from it really, they didn't see each others pictures ect. For me that wasn't cheating IF it was really anonymous. As for me it's not that much different to watching porn.

I was pregnant when I found out that it wasn't anonymous, he was sending pics and videos of himself and recieveing them too. He denied it but I had seen them. He would chat on this thing even if I was in the same room as him.

He then met up with some woman in a park during the pregnancy too. And I had to catch him out there for him to be honest about that too. I just noticed he was texting and texting someone on WhatsApp and happened to notice that it was a girl. Conveniently he left out the fact that he had a pregnant gf at the time and when he did eventually tell her she quickly disappeared.

A few months later I noticed him recieveing WhatsApp messages from another girl. I asked him about it and at first he denied it and tried to cover it up but I had seen him messaging her when I was standing right beside him in a pharmacy picking up medication because during my pregnancy I had blood pressure issues and GD. It turned out this girl was from his online sex chat.

Months pass and we took our son to Ireland for the first time to visit my family. And as I unplugged his phone from charging to plug in my phone I saw a notification for a dating app (Lovoo) which is actually how we originally met. When we were first in the relationship we agreed to delete it. He then told me he had just downloaded it to have a look and see if people still found him attractive. He never redeleted it I found out a few days ago he's still using it and that's almost a year after I first found him back on it.

He is claiming that I don't have sex with him enough. Like I did at the start of the relationship therefore its my fault he's doing these things. And yes it's true I've been sleeping with him less and less the more I find out he's chatting to others ect But would you want to have sex with someone who's constantly behind your back?