How to i act? what do i do? i need advice ASAP!!!?

ive been threw alot because of my mother. ive been hurt alot!!! im scared to let anyone near my heart and ive became bitter! im nice to everyone else but my bf!! how can i become a nicer person? how can i let this go and trust hm more and stop worrying? i cnt help it! i want to get rid of my bitterness please helpme!!!