Is there anything I can do to stop waking up before my alarm goes off?

Every day for the past three weeks or so, I’ve been waking up before my alarm goes off…and it’s really starting to bug me. I don’t know how early it is when I wake up, as my theory is that checking my clock will wake me up even more or stress me out so much that I won’t be able to go back to sleep, although I’m never able to go back to sleep anyway…I just sort of doze until the alarm eventually goes off. This only seems to happen during the week – I usually don’t use my alarm on the weekends, and when I do, I never seem to wake up before it goes off. I’ve also been taking melatonin before I go to bed for the past several months, as I’d been having trouble falling/staying asleep. But, again, this waking up early thing has only been for the past few weeks. I don’t think it’s effecting my alertness much during the day, it’s just really annoying me. Any suggestions for what I could do about it would be great.