this feeling

i have this gut feeling that im been lied to and something is going on behing my back, iv got this feeling a few times, nuthing happens to bring on this feeling and iv no evidance of anything but im usually right about it. the last time i got this feeling my boyfriend admited to texting another girl and telling her he loves her. the time beford that was an ex cheating on me. and now the same feeling again. i started to look into thing when i started feeling like this and i found out he is on a website tagged which i hear is mostly for dateing. his profile says in a relationship but why hasnt he told me about it beford. should i just ignor what im feeling and try move on or look into it more??