Possible cheating baby daddy

Today I went on my boyfriends Facebook to find messages from his cousins brother in law. The cousins brother in law was threatening my boyfriend with telling me that my boyfriend had cheated on me whilst I was pregnant and still is. Apparently he cheated on me with a prostitute!!! I am devastated! I replied on the messages saying that he was lying and how could he prove it. The cousins brother in law then tells me my boyfriend has been round his ex girlfriends mums house flashing his bits. My boyfriend is a gardener and the ex girlfriends mum needed her garden sorted out, so he went round there to give her a quote.

I can't believe it, apparently no one told me because they didn't want to upset me.

My boyfriend is saying it's all lies and he wouldn't do it to me!

I don't know who to believe, my boyfriend of 5 years and we have a 1 year old together. Or the bloke who has been sending the messages.

The only reason I am currently doubting my boyfriend is the fact half of the messages had been deleted before I had the chance to read them. When I was on his account he was receiving the messages, replying and then deleting them. Now I feel like he is hiding something.

I just don't know what to do, I'm so confusedšŸ˜­