First of all, I'd like to say good for you! Its one thing to decide we "want" to quit, but to go ahead and do it is another. You want to dive back in, but you won't. That takes SO much will power, its unbelievable.
So essentially, you're on day 3. Regardless of the last time you took heroin, the last time you took anything was 3 days ago. Thats where you count back from.
Typically, day 3 and 4 are the worst, so you should start feeling better by the end of tomorrow. The aches and anxiety should start to settle down, and you'll notice it just like that! To help ease those symptoms today and tomorrow, try taking a hot bath/shower and get outside, moving as much as you can. Its hard, very hard to motivate yourself but you've got to do it.
There's a thread at the top of the board titled "Sample Home Detox." Go take a look and use some of the suggestions. Nothing will completely take the withdrawals away, but there are many things that will help take the edge off.
Now for sleep... Go to the drug store and get some NyQuil or Benedryl. You may not get a whole 8 hours of sleep, but it'll definitely give you a few, at the very least. Right now, your body is looking for the opiate. The receptors are going crazy, searching for something, anything...thats why you can't sleep, thats why your body is jumpy, and thats why you feel so much anxiety. Well, the worst is almost over. You should be very proud of yourself for not diving back in.
Keep in mind that everyone is different. Some people have only 2 days of bad w/d's, while others may have 7 days. The most important thing is you have stopped. Just keep telling yourself "I can do this" and use as many suggestions from the sample home detox to make you less uncomfortable.
Good luck with everything, keep writing, as I'm sure others will help with suggestions too