Hey Travis.
Your situation sounds very similar to that of my 18 year old son, although his drug of choice isn't heroin, it's crack, and he doesn't suffer from migraines, although he might also be ADD/ADHD. I understand you're just a bit older than he is, you're about 20, right?
Like you, he doesn't have his GED nor has he ever held down any job for more than a week I think. He started using at about the age of 14/15...how about you? He has often said that he feels depressed and anxious though, and that he thinks he's gonna go insane, however strangely he doesn't want to take any 'prescribed' medications for it...like anti-depressants to help him get over this 'hump'. At the same time, he'll go entirely clean for a couple of weeks or months (not even smoking cigarettes or drinking coffee and remaining a vegetarian) but then he'll just whack out so strongly on everything he can get his hands on (crack, coke, 'E', special K, you name it).
The sad part is, there is nothing anyone else can do to help him. He can be offered help, but it's up to him to take it. It always amazes me of the heroic efforts he'll make to be entirely clean and just as things are going smoothly, he'll sabatoge his own efforts...as if he's trying to deliberately screw himself up. I don't know why this is, it just is. Inevitably, there is always a good valid reason in HIS mind why he couldn't keep the committment, go to a meeting, make an appointment, show up for work or whatever...he slept in, he had a bad cold, he was too depressed, his girlfriend broke up with him, the dog ate his homework...
The thing he's not realizing is that he's only hurting himself and no one in the real world will ever bail him out. No boss will allow him to be late for work every day. No teacher will give him a passing grade if he doesn't turn in his homework. No girlfriend will stay with him if he cheats on her. No friend will stay with him if he screws them out of money or lies to them. He's sincere in his desire to get clean, but he's not ready to deal with the most simple responsibilities of daily life. He's cried wolf so many times that no one believes him anymore.
I love my son and feel sorry for him and want him desperately to get better. Just as I hope and pray you will get better someday.
Unfortunately neither one of you will succeed until you commit to at least ONE thing for as long as it takes to succeed. In both your cases, I think, that thing you need to commit to is getting over your addiction and that does involve following a lot of rules and regulations that are going to be hard to follow. No matter how many migraines, episodes of flu, cars breaking down, dogs eating homework or whatever else may fall in your path to stop you...you must overcome it anyway and do it, no matter what. Just like when you endure the pain of a tattoo or a body piercing...amazing how a person can do that stuff, LOL, and yet miss the bus, miss the train or miss the ride to the clinic or 'forget' to take one's meds or just plain forget about oneself.
You need to care about YOU, Travis. You need to care enough about YOU to go through the crap to get to the good stuff.
My thoughts and prayers are with you, hon.
Nell
P.S. I hate to say it, but I agree with the others. You appear to be your own worst enemy and the only one screwing up your chances each step of the way is yourself.
You deserve better treatment from yourself, don't you think? 
I hate methadone clinics 
No job no money no money no meds no meds I'm screwed. It's like I'm running in circles and there's no opening anywhere.
