You should probably get checked out by a doctor just to make sure you don't have any type of illness or ailment that needs to get treated medically; there are some nasty things out there that can present themselves as heavy legs.
Assuming you get a green light from your doctor, you may need to adjust your training a bit. You're probably either over or under training. It's hard to tell from just hearing your situation because plenty of runners manage (and do well) running six or seven days a week, and plenty of others run every other day to give their bodies some time to heal up.
Some options you may want to consider:
- Take a week off. Go for walks, but don't play anything or train anything. Often times when you're training hard a week off can do wonders for addressing nagging problems.
- Sprints / shuttle runs. These are really hard on your body, but in particular hill sprints can really turn you into a rocket ship when it's time to hit the gas pedal.
- Plyometrics will help with your power output.
- A jump rope would be a cheap investment as well.
You want to beat up your body enough to cause adaptation, but not so much that you over stress beyond what you can physically repair. If you start training harder, stay on the safe side and put in more complete days off.
It's worth remembering that you get slower and weaker when training, you get faster and stronger recovering from training.