Melatonin making me super groggy in the morning. Major exam coming up.

So i have a major exam coming up and melatonin helps me sleep. I take it every night even though i have no issues with my sleep cycle but the reason i take it because it helps me fall asleep quicker and with upcoming exams i really don’t have time to stay in bed and wait for sleep. I’ve been taking it inconsistently since a year.

The dose i take is 1.5mg.

Now recently, since about 2 weeks, i started noticing that i’m VERY tired in the morning. I feel fatigued, i can’t focus. My brain is foggy all day. It’s getting very very difficult to study. Should i stop taking melatonin? Is it likely due to that?