What Could Be Causing Me To Get A Numbness Tightening

What could be causing me to get a numbness tightening lightheaded feeling In my head while lifting weights? I'm also experiencing headaches and the numbness is in my arms too a bit but not as bad as my head. Started when doing bicep curls @40lbs 20 reps per arm. I am 25 years old and in decent shape otherwise. I workout every day of the week for about 1-2 hours. I just got back into this routine December 22nd 2015 after not lifting for 3 years give or take. It's a decently heavy lifting routine heavy in the sense of lots of reps and lots of sets of lifting. Any idea as to what could cause this?