He proposed to me but treating me like crap:/

I thought we were okay and happy he asked my dad to marry. We have 2 kids together a 4 year old and 2 year old. We are both 30 . I am ready to settle and mature and i was never a cheater or liar. He doesnt let me go anywhere alone without him or the kids but yet he goes places alone and with his friends. I basically cant go anywhere alone to the store or doctors appointment he says he can take me but i need to go alone sometimes i need a break from the kids tooo like him. Also i cant even go to my own familys house without him and he cant go to his familys house or parties without me ... but yet he does whatever he wants and i get mad when he goes out but yet he still does it.. its not fair. Also i been noticing his phone he had a fake instagram account messaging little girls on there to hangout and smoke and drink etc.. i thought he loved me and wanted to marry me??? Why do i always get fucked over. 😔 all i want is to be happy with someone and for them to treat me and my kids right. I have been depressed and crying lately cuz idk why he does this to me..