I agree with Ashelen.
You need to go to the doctor to find out what is going on. The answer is that simple.
You need to go to your doctor and have them run a blood test. An increase in losing hair is actually not an indication of pregnancy....most women (75% or more) actually get thicker, fuller hair when they're pregnant and are less likely to lose it. You may be experiencing some sort of hormonal imbalance that's causing your irregular cycles and/or hair loss. You need to be evaluated by a doctor. Yes, you may be pregnant, but at this point you need to get checked out either way. They can run a blood test and/or an ultrasound and tell you if you're pregnant, but they can also evaluate your situation and see what's going on. Good luck!! (and yes, you CAN get false negatives).