HELP ME GUYS..PLEASE DOO...I DONT WANNA LIVE LIKE THIS ANYMORE?

Hey guys, i am a 16 year old bi guy i guess. I have done a terrible thing and its eating me inside. Whenever i think of what i have done...i always cry... Okey here's what i have done. In 2007 my friend told me about "i-mesh" a place to download free songs and chat with people around the world. At first my only intention was to download songs and thts all. But then i created my account and stated there that i am a 19 year old girl and i started chatting with other people. So there you can choose a country, so i chose India. And then i saw a guys name which was very interesting ( i am not gonna mention his name). So i clicked on his name and we started chatting almost EVERYDAY. Then one day he asked for my pic, and what i did was i took my couz's picture and told him she was me ( if you get what i mean) and to tell you all the truth..my cousin was HOT! SMOKIN HOT I TELL YA. Well then one day i recieved a offline message saying he loves me. And i felt the exact same way towards him. So at that time i was only 14 so i didnt taught of the bad things i was doing. But now i feel very terrible, i mean he wants to spend to rest of his life with me. We have been together for 2 years and 11 months. Everyday he keeps talking about kids and house and what our life will be after marrige. He has sooo much hope and he wants his life to be as he is imaginig it now. Everytime he says that i cry. I mean i COMPLETETY DESTROYED SOMEONE'S LIFE. I feel sooo terrible. And what i did was i told him that i have cancer and i may not survive. I did that so that i'll pretend to be dead and he can move on but he said that if i'm dead he will not marry someone else. And thats why i wanna ask you all there to help me...what should i do...god..i feel so bad...please people help me...i dont wanna live like this pleaseeee...i beg all of you....(crying)...please advise me what should i do...