What does the symptom of waking memory blackouts mean?

Recently, since entering college, I've been having panic attacks (even over little things that I know logically shouldn't stress me out), been getting so worried I throw up, and just a whole bunch of other things that are a bit unsettling but all of them I've just chalked up to being nervous since I'm just starting college and all that jazz, plus the panic attacks are nothing new since I've been having them since freshmen year of highschool (started when a friend died and then just kept going with other circumstances). But one thing that has started semi-recently has become really worrying and I'm hoping someone can explain it.

As of late, there will be times when I'll like have a waking memory black-out. For example, one time I was walking to class and then next thing I know, I'm sitting at my desk and I don't remember even entering the building, let alone the class room. And then another occasion was during a class. Like I started to take notes at the beginning of class and everything was fine for like the first 15 minutes but then, what felt like only a second later, the class was ending and I look down at my notes and I had only a half a page of notes (classes normally take at least two) and I had even stopped writing halfway through a sentence.

There have been about three other incidents of similar blackouts occurring over the last two and a half months and they can last anywhere from a couple minutes to an hour and a half if my guess is correct (because I have no idea how much time has passed exactly when I get out of the blackout and I have to form my guesses around observations). Also, right before the blackouts, like I'll have racing thoughts, and my heart will be pounding, and basically, it feels like I'm right about to have a panic attack. I don't really think I do much during these blackouts because other than the walking to class incident, I'm pretty sure I don't even move or do anything at all for that matter.

And if it helps at all, I take Adderall (adderrall) and used to take Yaz but stopped recently. Other than those things, I don't take any other medications. I don't smoke, do drugs, or drink. I'm 18 and have ADD, but no other diseases/disorders that have been diagnosed or that I know of.

But if someone can help me explain this I would be really grateful because, it's really begining to worry me and I'm incredibly worried about what will happen if this happens when I'm driving.