Boys advice needed!!!!!!!!!?

a few months ago i seen that my bf had phoned his ex gf late at night when he was drunk and also one of her friends, i asked about it and he said he doesnt remember and must have called by accident instead of callin a mate so i left it. it seemed to b more than a coincidence tho so i mentioned it again recently and he said he ***** believe i asked about it again and hasnt been speakin to me since. i want to know if u think he has been meetin his x behind my bk? he rarely kisses me nemore and is not as interested as he used to b bt doesnt seem to b too secretive. am i just being paranoid?