I injured my spinal cord in two spots seventeen years ago when I was 13 years old. Nowadays if I stand up for longer than ten minutes in 2 hours, or bend over much at all, the cord starts to tingle, as if it is being tickled with a feather. This is like a warning sign. If I don't immediately lay down and stay down, I then feel a soreness there, and that is followed with sharp pain, then I feel like a sumo wrestler just wrapped his arms around me from behind and squeezed as hard as he could. This makes it very hard to breathe. After this, if I don't stop everything I'm doing and remain motionless on the bed, floor, couch, etc., I suddenly become weak and all the feeling from my navel below disappears. I then fall to the ground so suddenly that I often don't have time to protect my head.
This paralysis lasts from a mere 30 minutes up to 5 days. Even after I regain movement and feeling, I must remain very careful or it comes right back. I have one lower back injury, one upper back injury, and a neck injury. The lower back one causes the paralysis, while the upper one cause breathing difficulty but does not paralyze me. The neck injury, when it gets sore, causes everything from my neck down to become very weak, including my arms, of course. So I can't break my fall when my neck and lower back act up at once. The amount of weakness the neck injury causes when acting up is bad enough that I can't lift a half gallon of milk with either arm.

I live with my parents due to this and other disabilites. However, they are obese and cannot exactly carry me around when I'm paralyzed. I also can't pull myself along the floor with my arms since they grow weak. I've hit my head many times, but have not suffered any severe injuries as a result, thank God. However, my parents are greatly stressed when they find me in the bathroom or something, on the floor, motionless. I can't yell out, and many times what causes my lower back to make my legs stop working is just using the bathroom. So I'll use the bathroom, stand up, then fall and they'll hear a loud SLAM. Next thing I know, I'm being told I had knocked myself out hitting the floor/wall on the way down, and since they couldn't bend down to move me, they had to leave me there, but brought pillows. You can imagine how much this stresses them, and they don't need such stress.

Do any of you know anything I could do to help prevent my injuries from causing me to collapse as often as they do? I know it cannot be fully prevented, but just a little help would be nice. I can't help my parents clean up or anything since I can't bend over, and I'm the only skinny person here in the house. My dad doesn't fully realize how weak my back is. He's my stepdad, since my first dad died in 2004. When I was 13, my first dad witnessed me injure my back and saw me become paralyzed for quite a while. I'd even sneeze, which would cause the muscles to tense up, and then I'd be on the floor unable to move. I couldn't get out of my chair without help either. However, my stepdad seems to think I'm faking it to a certain degree, though soon I'm having many scans done on my body, brain included. Maybe then he'll understand. It's just frustrating for one of your own parents to doubt you like that. 

So that's one reason I want some advice on it. I want to be able to help my parents out, and not be doubted by my dad. I use a back brace, knee braces, a cane, and a walker when needed.
Is there anything else I should try?

Thanks in advance!