Should i trust him

Me and my partner have been together for 16 months back in June, he started spending a lot of time with a girl at work. Always messaging her when he home then started being on his phone all nite while in bed.

Then he rang up while he was at work and told me that people where spreading rumor's about him sleeping with this girl.

Then he finished work but everyday she wud turn up at our home or he would make a excuse to go to hers.

We then moved away and I had another message saying he was sleeping with this girl. Every time she rings he takes the call outside, he moves his phone away from me and keeps his phone on him.

Now he keeps going to my sisters at the kids have gone to bed to do jobs, like tonight his changed his boxers before he went and put more spray on. Can I really trust him?