How do I stop obsessing over my bf past and stop attacking or making arguennts

Just as the title explains. More insight, my bf uh two weeks ago did lie to me for 10 months abt his interactions with his ex and girls although it was very minimal contact. *** maybe this has smth to do with the way I am behaving with my bf. I notice I start arguments, assume, obsess over his past and always want to find smth. But this has been happening before him and i am a very insecure person and was hurt in the past- i never seem to take a breath and i just say stuff or assume stuff or attack my bf without knowing anything. like today i snooped around and he friended his ex on roblox and i got scared and hung up on him but it was when we weren’t together bc we thought we be better as friends but i began to overthink. and i made the decision to break up or a break on the spot - i am thinking of a break right now that way my bf can have a breather and maybe i can break this cycle. ? is this a good thing to do? how do i stop this? i think i have a lot of underlying issues