My bf is acting strange is he cheating

So my bf started to act differently a few days ago accusing me of lying and cheating randomly out the blue we’ve been together for 6 months he said he felt like we rushed into things even tho 5 mins earlier he told me he wanted to marry me one day there’s been rumours going round that he slept with another women he denies these he Also told me he’s stressed because his ex rang saying she wanted to see him when he gets back and he’s sick of her pestering him but he told me previously his ex was chatting to his freind and that his freind invited him to a party and that she would b there then he told me he was going to another part of town and his freind was chatting to another girl he used to chat to and she might be there I’m confused