Please help me out?

i m 22 years old male and i have a problem that i dont take interest in any thing i dont know why when i start doing something like i used to go to gym n guiter cles and then after a mounth i left it i dont know why may be cause i am fat and i smoke alot even my stepmother tells me why u dont take interest in anything n then i say her i dont know why.. i even dont have a girlfriend i liked to have one too but how. please help me someone ill me much thank full