How can a man go from being so perfect to a nightmare in just 4 weeks?

How can a man go from being so perfect to a nightmare in just 4 weeks?
I’ve been seeing a guy 2 years, living with a year.
For the past 7 months every 4 weeks we split up it’s crazy! Starts with him crying / begging me back – promising it won’t happen again – I’m his world – never met any one like me – crazy in love – I’m beautiful etc. etc.
He’s just perfect for 3 weeks then cracks start from him giving me silence treatment – I can feel tension – he will say his piece with an attitude, I will explain in a quiet voice it’s not me it’s you ..
He then raises his voice blaming everything on me, then screaming in my face with gritted teeth – clenching his fist, calling me a c **t and other names – I keep silent not to upset him but that makes him worse – if I say anything that also makes him worse. He’s thrown me about in the past, got in my face in an aggressive manner in front of my kids. Controlling, can’t have friends. He doesn’t like my eldest child coming round I can feel it. And each time I kick him out feel strong he begs – cries – pleads – to start all over again. I feel so drained kicked him out once again blocked him as I always do but he uses other phones. I need to stop this. I know I do, but why am I so stupid to let him back?