Is he cheating?

Been with my boyfriend for a month officially (when we made it Facebook official 😏😂) but been seeing him for about 5/6 months now. 
When we argue he often will say "I don't know why you're with me, you can do better"
Or "if you want too go shag someone else, then I'll let you"
I am 100% happy with him and adore him. 
I'm just wondering if maybe he's cheating and feels guilty, so he's telling me too go and sleep with other men. 
Any thoughts ladies?