i fully pump it and when i ride around for a little bit it isn't as strong as i would like it to be. There isn't any holes or punctures. Is it a tube problem? if so any tips of fixing or replacing a tube?
I say its the tube, mite be punctured (the tube) I suggest going to your local bike shop and bying a tube.
Tips on Replacing-
Its easy really, use a butter knife to pull the tire off (w/out poping it) and slide the tube in then put the tire back, V-WALAH! Hope that helps...