I'm certainly not qualified to answer this but with God's grace I have to try....
To begin, medications are synthetic and could have suicidal side effects as well as side effects that cause the stomach issues, I'm no doctor just giving you a heads up, you might want to research your medication's side effects judiciously. Also, believe it or not, a little extra water, fruits and veggies should help balance you better internally. It's all about balance and moderation.
Depression is a powerful powerful enemy, but you have the one thing in your possession that defeats it every. Single. Time. That would be God's love.
We are all worthless, broken humans wandering, what appears to be the devil's domain, so with that comes the devil's hatred of us (because the devil's a loser, he knows it and God knows it). With that hatred comes all the satanic attacks on us, In your case they translate to bouts of severe depression and cutting.
Our body is God's temple, I'm not surprised Satan deceived you into thinking that harming your temple would bring relief, but sadly it's a false conclusion.
Life is a journey, not a point in time. Nothing will ever be perfect but we must choose to carry our crosses, like our savior Jesus Christ or simply give up. I don't know about you but there are SO many mysteries to this existence I'm obsessed with learning truth each and every day, it motivates me. I also prayed for wisdom and received it. I'm eternally grateful but I didn't heed King Solomon's advice: with wisdom comes great sorrow.
I'd like to finish on a high note though because, I don't know about you, but where I live Winters stink and spring is seemingly about to break through. Did you know, right now, you have 2 amazing resources at your disposal to defeat your problems? They are: prayer and the Holy Spirit.
Pray daily, to God, with a sincere and contrite heart, mean every word you say, ask with the right intentions and never ever give up. Gods timing is not the same as ours. In your prayers, be bold enough to ask for the Holy Spirit to directly intervene and help you. I will keep you in my prayers and I hope you have a strong support network of friends and family too.
And please don't ever kill yourself, life's too short as it is... You're 15, life's not easy but it sure can be exciting at times. But you have to get a driver's license first, go-to college and strive for all the other blessings in life like love, marriage, family.
Last thing, remember God sent his only son to die for us and take on all our sins, I don't know about you but I feel like I owe him an honorable life in return for such a gift. Have you heard of the term God's grace? If you have, like me, you might not be able to exactly define what grace really means. Well I heard this awesome explanation one time that I never forgot....
God's
Riches
At
Christ's
Expense
God bless you and I hope you found some comfort and solace in these words, I'm rooting for you now, I love an underdog ?