I found a pink bath towel in my boyfriend's room.

It's arbitrary to suspect him of cheating just because of a pink bath towel. If he has less contact with you at ordinary times, his tone of voice has changed and he is a little impatient, then nine times out of ten, he is cheating. He is alone abroad, and it is easy to cheat when he is lonely. If you love him just to vent, forgive him! It is not easy for him to be abroad alone.