When does a less than desirable sleep schedule become insomnia?

I’ve always been a night owl going to bed between 1 or 3 in the morning. But over the last month and a half or so I’ve been un able to get to sleep till 6 in the morning or 3 in the afternoon on school days. I’ll lie there in bed for like 45 min till I give up. I go some days without any sleep at all. Even though I sleep at odd times I usually get 6 hours of sleep which isn’t that horrible. I only really worry because I have seizures and lack of sleep kind of influences that. So I’m wondering if it’s a problem that I need to go to a doctor for or something that I’m blowing out of proportion (I’ve boon known to do that)