Windows 7 myriad of problems. PLEASE HELP!

Alright, so I have a serious issue. As of the past few weeks, my computer has been acting up. It's been randomly BSOD'ing, moving slower than usual, and sometimes the computer would crash but there wouldn't even be a BSOD, it would just cut to black and then go into the startup process. Despite all that, it would go for periods of hours working just fine before restarting. Now, however, I seem to be stuck in a loop of problems. When I boot into Windows 7 normally, it will either let me log in and just show me a black screen with my cursor on it but nothing responds, even task manager does nothing. Other times however, it will go to my regular desktop but the computer will go extremely slow and whenever I attempt to work with a program, it will go into the "not responding" mode. I was able to boot into regular safe mode once, and my mouse worked fine but I wasn't on networking safe mode so I could not go online. Then, when I attempted to go onto networking safe mode, it would freeze on the 'loading files' screen on a file I can't remember the name of at the moment. Now, I've finally been able to boot my computer into networking safe mode, but everytime I do my mouse stops working! It's one thing after another! I've run all the tests that windows 7 allows me to run, and each one tells me nothing is wrong with the computer. I did run a chkdsk recently that told me it deleted some corrupted files and such, but it didn't do anything to help. Working without a mouse is severely limiting the things I'm able to do, and I really have no idea how to solve this issue. I don't even know what the issue is, to be honest; googling it just gave me all of the problems i'm experiencing, but separate. No one ever seems to have experienced every single one at the same time. I really don't want this to be an issue that ends up with me losing all the data with my HDD so I haven't attempted a full system restore, but I also really need this computer to work as it's my only source of income. Please, anyone who can help I would appreciate it more than I can describe with words.