I love the determination!
but hey, were you starving yourself the first time. because don't. I'll assume u are a male, so listen. u can still weigh a 100kgs and look the better than you ever did. the KEY is your DIET. Follow a high protein diet all the while minimising your carb intake. if now u are free from the clutches of your studies, do workout for best results.
I'm repeating again. DO NOT STARVE YOURSELF. Because once you do that your metabolism will get fucked up, which means your hormone balance will get fucked up too. moreover, no matter how much you workout you won't be gaining any muscle because there isn't any protein in your diet, the wear and tear in your muscles can't be recovered. also, body starts using up muscles for energy when there is not enough lipid(fats) in your body.
so, if you are really serious about doing it right this time, make sure you plan out your diet. Remember to get your RDI first.