I took 2 mg klonopin (clonazepam) and 18 mg of melatonin not knowing i wasn't supposed to mix the two. is there a chance i won't wake up? i'm worried :(

I would only expect a minor interaction with the low dose of klonopin., the reaction being possibly only a sounder night's sleep. In other words I don't think you're in any danger or need to do anything at this time. If you're still concerned & have a partner living with you ask him or her to awaken you during the night if you're in a very sound sleep.