Generally an individual cannot be prosecuted again for the same offence once he has been found not guilty at trial.
This was a problem in the matter of the murder of Stephen Lawrence. The family took out a private prosecution against those whom they thought were responsible. They were found not guilty and a new prosecution could not be brought, even though the case against them had become stronger.
Recent changes to the law (largely brought in as a result of the above) do now allow for re-trials in certain circumstances. The offence has to be of a serious nature and �new and compelling evidence� has to be forthcoming which was not available at the first trial. I doubt that the circumstances you describe fit the bill.
Your only course of redress is to take a civil action against your tormentor. The �burden of proof� in civil cases is lower. You have to show �on the balance of probabilities� that the acts were committed � that is the judge has to be 51% certain that they are true. In a criminal case the matter has to be proved �beyond reasonable doubt�.
The downside is that you can only claim damages for injury or distress (or whatever you feel you have suffered). If the case is found in your favour, the individual responsible does not receive a criminal conviction and cannot be punished by means of imprisonment or a community order. He can only be made to pay you damages, and these may prove difficult to recover if he has limited funds.
The other thing to consider is that you will almost certainly need representation to have any chance of success. It is doubtful if you will receive Legal Aid and your costs could be considerable.