How can i stop being paranoid??!!?

I have a wonderful boyfriend who i love totally... but i am messing things up with my jealousy and paranoia.. i have always been cheated on by past partners and although i have no reason not to trust my current boyfriend, i cannot help but worry all the time!! He puts up with me but recently i know he has been on the brink of ending things due to the way i am... this breaks my heart as i see that he is not only frustrated by the way i think but also hurt because i dont/cant trust him! i also have a child from a previous relationship (whose father was violent - i left him because of this and despite never standing in his was, he has never seen his child - he doesnt even know when he was born as i left when i was pregnant due to the volence) and although my current partner is wonderful with my little boy (2yrs old) and says he has no issue with me having a child at all, i still worry! i really need coping strategies to deal with my insecurity - help!