A couple of times I masturbated twice in a row and sometimes I can't seem to climax on the second time. Is this normal or should I be worried (I'm a guy BTW if this helps)?
Yes it is normal. There are lots of men, all of them for the most part, who can rarely if ever do if one time after another. A hour later - lots of guys can. But once then again- very few - except when they are under about 24.