Oh god I definitely feel your pain. Constipation is something I also deal with in my life. I usually have a bowel movement right after I finish breakfast in the mornings, that's like my window of opportunity to go. If it doesn't happen in the morning, I'm unable to go until next morning (hopefully). Last month for some reason I had a bout of constipation that lasted about three weeks. It was absolutely miserable. I didn't want to take laxatives so I did everything else - prunes, squatting, lots of water, etc. My diet was already pretty clean to begin with.
Finally after weeks of only having 1-2 bowel movements, I decided to take three Ducolax stool softeners. I also did a lot of research and found that apparently, magnesium is important for bowel movements, which is found in cocoa powder. Fats are also helpful for digestion (bile production and all that), and I found that some people recomended taking a spoonful of pure olive oil in the mornings before breakfast.
So I took one stool softener at noon, and two more at 9pm. That day I also had some yogurt and some ground flaxseed. The next morning, before I ate my breakfast (one sunny side up egg), I took a tablespoon of olive oil. Ate my egg, drank my hot black tea (hot liquids help you get that urge to go), and a few minutes later I was able to have a full bowel movement! That day I went I took two more stool softeners just to make sure the next morning I was able to clear everything out.
I fear getting constipated like that again, because for those three weeks I felt so uncomfortable everyday, and it was mentally stressful. I felt so debilitated. So since then, everyday I will drink at least 2.2 L of water, and have my yogurt mix of sugar-free yogurt, 1-2 Tbsp of flaxseeds (ground up), and a Tbsp of unsweetened cocoa powder. And everyday since then I've had a pretty hefty bowel movement. The flaxseed definitely helps in providing bulk to your stool and soften it, as long as you drink enough water everyday. I also make sure I have some papaya after a heavy meat meal. Fiber and veggies are somewhat important, but not as important as it has been made out to be.
I would advise you to take some magnesium citrate to clean everything out as well as some stool softeners, since it sounds like you have a lot of old impacted fecal matter in there and it may be too dried out to get it out through usual methods like prunes or healthy eating. If it still doesn't come out, you should really see a doctor!! Then to prevent it from happening again make sure your diet is clean, and drink lots of water everyday. Make sure you get enough magnesium in your diet, and I would recommend a daily serving of yogurt (no sugar added!) and flaxseed, only because I've found that it has definitely helped me stay regular. Yogurt for probiotics, and flaxseed to help add bulk to your stool and to help soften it. Good luck, I hope you're able to resolve this issue. I know how horrible it is! :(