Why do I nearly pass out and go numb?!

Why do I nearly pass out and go numb?

So this is kind of weird. I love excercise and enjoy going to the gym regularly. Usually semi-heavy weight training. Sometimes other aspects of life get in the way and I don't go to the gym for two weeks or so. The first few days I get back to the gym, this has happened probably four or five different times, I will excercise and at some point nearly pass out.
Sometimes it's after a difficult excersize, other times it's been after I leave the steam room when I'm showering off.
The actual occurance is like this. I'll start to feel a little light headed and I'll decide I need to sit down. I find a seat, and sit. Then I will get better. As I get better, I have tingling in my fingers, arms, and legs. In the steam room as it's coming on, I will also have tingling in my bottom jaw.
When in the shower, or leaving the gym, I have to walk more than a few feet to find a place to sit. This seems to make things horribly worse.

2 weeks ago
Months ago, I returned to the gym after not having been for two weeks. While working out, I worked out with the same intensity as normal. I know that probably wasn't a good idea sure, but I did. I felt light headed and decided to leave. When I got out of the gym doors, my car was about 40 yards away and I decided I wouldn't make it. I sat at a bench for a few minutes. Then I went to my car. As I walked it got worse and worse. Tunnel vision started to set in and by the time I was nearing my car I couldn't see anything. I got to my car managed to get it unlocked and fell into the car onto the seat. After laying and resting for about five minutes, I felt drained, maybe from this, maybe from working out, but I essentially felt fine and was good for the rest of the day.

2 weeks ago
Today I decided to post this question up because I think it's the worst it's ever been. I started to feel the tingling in my jaw in the steam room. I got out and went to the showers. I stood there and felt more and more light headed and new I had to find a bench to sit in the locker room. I made my way out of the shower, down the hall, and then somewhat passed out I guess because I then realized I was on my knees falling forward. I cought myself with my hand but did hit my head on the floor. I remained concious enough that I didn't end up completely on the floor. I pushed myself back up and made it to a bench where I sat for about 15 minutes and was feeling pretty good. Then I rode my bike at a slow pace 3 miles to home and had no problem doing that. These fits seem to be completely isolated.

Could this be a form of heat stroke? I also have pretty low blood pressure. The doctor says as long as it's consistantly that low it's good, and it is, but could that be a cause?

2 weeks ago
I do have issues sometimes sitting on floors, with legs crossed, or even straight out, or my arms out where they will fall asleep much more than it seems is normal for other people.

2 weeks ago
I never feel like I am short of breath before, during or after these fits.

Make an appointment with your family doctor, before you continue exercising, for a physical and some simple blood tests. The doctor should check your sugar and iron levels, and do a complete blood count (CBC) and complete metabolic panel (CMP). The tests come back fairly quickly and the doctor should be able to tell you what is going on and what to do about it or maybe will send you for more tests.
Just please don't ignore it...Good luck.

p.s. You should go through a stress test as well in case you are not getting enough oxygen. You will not necessarily feel shortness of breath from oxygen deprivation.