As previously mentioned....this is all guesswork. Bloodwork would make this much easier. You almost certainly crashed your estrogen. Did it rebound.....hmm.....well who knows. High and low estrogen are very similar symptoms.
As far as the test injected, I'm assuming this is 3 shots at 250 each.....totalling 750 in a 10 day period. Well yes....when that hits your bloodstream your body will compensate by lowering your production amount. I would get bloodwork now....and probably monthly until I felt I had stabilized. And if it were me........I'd take clomid for a few weeks. I respond very well to clomid, as most men do. I like 25mg per day.
Very few people do what you have done.....so advice on it is hard to give. I'd bet most people would ride it out.....maybe use some.of their pct gear...then back up their approach with bloodwork.
Again....good luck bro. Let us know how it goes. This is how we learn.