Sounds definitely like an infection. There can also be germs in the bag that the drugs come in, not to mention what you gear is cut with or made with, what they have cut it on, the spoons your using etc etc
As I have read on.... you are shooting pills, pills that are now made so that they cannot be broken down to be injected, heat causes it to glug, so does cold water, not to mention that if you re use needles, you probably are careless with filtering what is there. Seriously, you are wasting your time.
MAYBE, you gone straight through the vein and missed and injected into the muscle tissue, not realising? When you are keen for that hit I guess pain and the fact that you are making a mess of your arms can become the least of your worries. but injecting a thick gluggy solution can only result in what your have got with your arms red sore and lumpy.
I always treated injecting it as If I'm going to be sitting down at the dinner table across from my family the next day. You want to leave no if any marks possible.
I can say I have experienced what you would call a "crunchy" feeling but is wasn't painful and was scar tissue that had built up in the area. All comes down to ALWAYS using a clean needle, and never re using, Change the vein you are using, If you are talented enough to be able to use the other hand, then even better, it gives your main arm a rest for awhile.
I do agree you need to see a doctor blood infections are bad, and people die from the bacteria in the blood.
The best advice I can give, is give up. I know its harder said then done, but there is more to life then being high. I'm far from religious but once you find your reason to be here, you will understand, until then, be safe and try to find out what can and cant be injected.