I am 24 my penis not tight during sex

I’m not quite sure what you mean by your penis not being tight. Do you mean that inside your partner’s vagina, there seems to be more room than you would like? If so, that may be just a matter of becoming used to your partner’s body and learning how to shift yourself and get in positions that provide for more stimulation. It could also mean that your penis has become somewhat de-sensitized; try using a top drawer penis nutrient cream (health professionals recommend Man1 Man Oil) with acetyl L-carnitine; this is a neuroprotective ingredient that helps avoid peripheral nerve damage and maintain penis sensitivity.  Good luck!