need advice and opinions?

[mommy of one]

i have been dating a guy for 5 months and i love him, but recently i got a letter from my ex-fiance who was drinking and taking pills. he says that he has been clean for awhile now and wants to start dating again. he says that he wants to show me what he should have showed me when we were together. he tells me he has been going to meetings and realized that he had a sickness. he had a rough child hood and was covering it all up with drinking and pills. i still love him and have never really gotten over him. when he was sober he was the greatest man i had ever been with. we were together for about 2 years. i dont want to hurt the other guy but my heart keeps telling me to give my ex another chance. i thought that i was happy without him but now that my ex has been sending me letters i find myself getting shaky and butterflies in my stomach when i think about my ex. pleast help