Ex boyfriend

So me and my ex boyfriend have just started seeing each other again after he ended it with his girlfriend off the time to sort things out with me. But while he was with his girlfriend he cheated on her with me, I don't know if I should trust him or if I have a right to be paranoid but he has also been texting his ex girlfriend a lot since we have been talking but he says there just friends. I don't know what to do I need advise do I trust him or not 😪😪