No offence bro but you are so green it's not funny
Taking a prohormone will either be the biggest waste of time or the dumbest thing you've done to date. A simple test cycle is safer then a lot of prohormones (putting my flameproof jacket on) and at a reasonable dose will produce less sides. Dont for a second think that because these products are legal that they are anywhere near safe or you can just take them willy nilly like something from your local health store
BUT. You shouldn't be going near anything at this stage. Most supplements are junk, yes but to you I would suggest getting a zma complex and some fish oils. Lift heavy, train compound lifts and realise if you cant grow naturally at your weight, drugs are goin to do nothing (nothing permanent or nothing altogether)
If you're not gaining weight and you cant stomach any more, add more healthy fat to your diet (it'll positively affect your test as well)
Once you see regular progress and learn to break plateaus naturally through diet and training, go and do some research on ph/aas and by some research I mean 6 months+, think about every side you could come across and have a plan of attack for all of these
Good luck....