Plumbing woes - Help!

Plumbing woes... what makes the toilet NOT fill up with water in the back, so that it can flush? Since last night, we have been having this problem and I cannot for the life of me figure it out. The water just barely drips into the back part where the water is stored. It takes hours for it to fill, and even then it will not deliver a full forced flush. Everything looks fine - no kinks in the chain, etc., but then again, I do not truly know how things should look. Everything else is draining fine, well, the tub is a little slower than usual, but that's all. If the problem were a clogged line, then the toilet would run over, correct? Any possible solutions would be welcomed as I do not have the money for a plumber.