First try leaving the computer to try to recharge overnight, without your troubling it. Sometimes it can take quite a while to show progress if you've let the charge in your laptop go completely. If that doesn't work, see if you can borrow a charger and try with that, in case the charger has become faulty. Next, do the same with the battery. Borrowing is much cheaper than buying at this stage, so if you can't borrow, miss this step and go to the one below.
If all of the simple methods don't work, just have it properly diagnosed by an expert. When you get into that asking an opinion online thing, you will most likely end up with at least 20 non-expert opinions on what the problem is, and most of those will be poorly explained and can leave you with further problems and you'll STILL have to take it to an expert.