I'm not really willing to call you an idiot, sorry.

But I do very much agree with the part of your thoughts that see OD'ing will not make things better.
I'm thinking two points here
a) strategies for making it harder to impulsively OD
b) strategies for better ways to meet the needs you try to fill through OD'ing
I wish I could tell you "this is how to fix this situation" but I can't, I'm struggling with the issue myself. But some questions:
a) What can you do to prevent yourself from having tempting pills around?
(for me, this has involved not getting prescriptions for meds I'm likely to use, return surplus meds to the pharmacy, and asking my b/f to clean out unnecessary OTC stuff)
b) Can you make plans in advance for how to get extensions for assessments in other ways, such as through talking to teachers or tutors?
Check around, what do people who don't OD, SI etc. do to deal with those situations?
Other ways to ask for help? Talk to people? Write them? Make a deal beforehand with people closest to you to use a "code phrase" when things are too hard for you to cope with alone, and what to do to help you in that case?
Can you schedule breaks for yourself? It can be hard to accept in this world of constant press for achievement, but we all do need holidays from life now and then. A weekend maybe, without school or work or even planned socializing with friends.
Can you get the danger buzz in any other, less damaging way? Extreme sports? Travel? Games?
(I personally love the danger buzz from OD'ing so I don't find it weird... )
To break the normality feeling, I have studied up some on the physical danger details - but I realise this could also backfire, so I don't know if it's something to recommend everyone.
It sounds like a positive step to me that you are looking at the situation at all, and thinking about it now before it gets out of hand. I really hope things will work out for you. OD's are nasty business.