What should i do?

Ive been with my ONE of my boyfriends for almost 4 years. I love him very much but theres also a lot of pai n..just this year i met this new guy...who is now my 2nd boyfriend and he treats me so good and im startin 2 have feelings for him. I tried to break up with him but its hard. Iwant 2 b with my 1st boyfriend more but theres no excitement betwwen us like me n the 2nd..its more love..what should i do?