Since you discontinued your injections in August, and it is now December, I would encourage you to seek the opinion of a gynecologist. You need not return to the physician who encouraged you to take the injection. You can (and probably SHOULD) find a new one.
In my experience, the symptoms you list could be attributed to any number of other things, outside of side effects from the discontinuation from these injections. I would guess that it could take your body 6 months to a year to recover, but it's possible you could have symptoms that last you a lifetime, too. (I have not taken "depo" but was given a Lupron injection once well over a year ago, and I still have side effects from it.)
You're tired because you are constantly bleeding. Even if it's not a lot all at once, it's nearly non-stop. If nothing else, see your primary care doctor and get your iron levels (including ferritin) checked to look for anemia. That's at least a place to start. If nothing else, treating the anemia will give you some energy back.
The fluttering sensations can possibly be attributed to strange new gas, which could be the result of the growth of fibroid tumors on/around your uterus. It could also be the result of malignant tumor growth, though (which is a concern). Or - a result of endometriosis. Or PCOS. Or adenomyosis. Or endometrial cancer. Or a serious infection. This is also true of the bleeding, the nausea, the lightheadedness, the bloating, the aching, the back pain and the cramps. If fibroids are your problem, you have clearly reached a point that treatment of some kind would be beneficial. If these are the cause of your trouble, be advised that any physician who tells you your only option is hysterectomy (or says only hysterectomy or uterine artery embolization) is WRONG and is NOT the right doctor with whom to pursue treatment.
Please find a gynecologist who will help you discover the source of your discomfort -- and who hopefully will also help you find a solution. Sometimes it would be the most benefit to see a reproductive endocrinologist, as these gynecologic doctors specialize in problems of the reproductive region.