why does this Aries guy keeps coming back?

i am a gemini female i been dealing with this aries guy on and off for 8 yrs now.we dated for 2 yrs broke up. then stayed friends with benefits. i then decided to move on with this libra guy,but i still felt something for the aries guy. i couldnt forget him, then a year later into the relationship with the libra, aries pops up outta no where. at the time i was pregnant with the libras child. so i didnt meet up with the aries.he was crushed when i told him i was pregnant. he then moved away accross the country.he lived out there but still remain in contact with me, he was in a committed relationship telling me theres nobody like me for him.he would come visit through out the yrs. he then had another serious relationship and still would call me and then tell me the samething. finally after 5 yrs he moved back. and we decided to move in together. a 1 month and 1/2 later. i was fed up with his bs and told him he had to go. he left. i thought this time it was truly over. 3 months later hes callin me again wanting to work things out, "bacause am the one for me" now why does he keep coming to me? is this normal?

Because you keep letting him?

Whether or not his behaviour is normal is not the issue. Whether or not his behaviour is acceptable for you should be your concern. I honestly don't understand why he's acting like this, since it's obvious he's hurting you and, you know, when you care about someone you try your best NOT to hurt them. I can think of a few possible explanations such as: he thrives on your attention, he is not able to have a functional relationship with anyone and, each time he fails in an attempt to, he returns to you, or maybe he really does have feelings for you but he also has issues - and serious ones, at that.
I'm not really sure whether you're actually asking for advice. But if you are, here's what I would suggest. Sit down and think hard about what you want in a man and in a relationship, assess how much of his behaviour is or isn't acceptable for you, then call him and talk about it like two grown-ups. It seems unlikely that he might not be aware of how much he's hurting you, but it's an option you need to consider. So, once your ideas on the subject are pretty clear, go ahead and lay your cards on the table and see what that gives.
A word of warning, though. Aries are known to love the chase and lose interest as soon as it stops being challenging. However, if you find yourself in that situation, give it up altogether. It wasn't you, it was DEFINITELY him. You deserve someone who likes you and enjoys being with you and wants to BE with you, not just chase you whenever you become unavailable.
Best of luck.