Assuming this case is genuine you cant go saying nasty and silly unhelpful stuff like "try it". I don't know how serious this guy is, if at all, but why take the chance, you could have a lot on your conscience. There's times when everybody feels low, and as cheesy and cliche as it sounds it does get better and people who've had a lot of cra ptimes in thier life and get over it arew better equipped should they get themselves out of the rut, and imo can really appreciate the great things in life a lot more than those who've always had it easy. Bear in mind there are people who are a lot lot lot worse off than you, and people who have no choice but to die, would it really be a wise and fair thing for you to do.
You've got to focus on the positive things, life is never going to perfect, but from what i've read of your post, you've got a dad, and a roof over your head, and have loved someone, and are in a good English university which is a lot more than a lot of people have, some people would count you as so so lucky! You say your dad doesnt care but i can pretty much guarantee you he'd be gutted and it would ruin his life if you killed yourself. My parents have bitchy digs at me but its only because they want the best for me , and me to do the best i can, so i take it on the chin and try to prove them wrong. Seriously though, don't do it, just because you don't have to face the consequences there would be a plethora of people who did, including your ex gf who you said you love, if you really loved her would you put her through that, all her life thinking maybe she was to blame for your suicide?