My last mens date 8th january, i have 8days delayed and i've lots of cramp for 3days but there's no blood.. what should i do?

Check test: Check a pregnancy test first to make sure that the delay isn't due to pregnancy. If you're not sexually active or test is negative, then not much you can do other than wait. It's possible to see a doctor and they can provoke a period with hormones, but they aren't likely to do that unless you are in a lot of pain. Likewise, if you desire regular periods, then birth control can help regulate.