always feel like i have to pee, been consipated a lot lately, headaches, lower back pain

hi, im feeling slightly confused at the min, could someone give m an idea of what could be going on? ok here goes ... i always feel like i have to pee, i have been constipated a lot lately, headaches over the past couple weeks especially in the morning when i wake but they are not occuring as much as they used too, i have lower back ache that comes and goes but it is not sore just annoying, i am always very warm ( i am never this warm, im usually always cold), i came off the pill(dianette)nearly 5months ago and have had a period every month since then, they have been quite regular since i came off it ( they were irregular before), if looking back at last month then lthis month is late but not sure as they are not totally regular! I have had unprotected sex a lot as me and my fiance don't mind if i become pregnant as we would be happy. I took a pregnancy test but was negative so assuming im not! But could someone please help???? ...oh n im always losing my temper a lot lately!! (more than usual)

Thanks

You could be severely dehydrated. See a doctor though. Could be serious.. but most likely severe dehydration.. drink 2 litres of water a day.