[Google]

Try starting the gym and go regularly, also make sure you're eating properly.

I am going to training daily if not a day I am running, so I stay fit.

It's not supposed to be easy as you grow up.. You just need more effort.
If you really like what you do, you shouldn't get bored of it, try to explore new sports maybe?

I am not bored.
I sometimes do not have the stamina to do the sports.