Not every situation in life appears to be as simple and good as it seems... one among them is harassment at work place... one of the most weaker situation of our's could become the strength of our colleague or boss and he could harass you to fulfill his desire, at the cost of your job/promotion/any secret if revealed might cost your job or even your committed relationship...

Whatever might be the reason, rather than letting yourself being harassed and being guilty for the situation, it is far better to do your bit to come out of it... after all, 'nothing' is important than your peace and satisfaction on leading your life;

You might be able to resolve the situation quickly yourself by explaining to the person who is harassing you that their behaviour is unwanted. 

Make sure you're informed - find out what the organisation's policies and procedures are for preventing and handling sexual harassment.

Keep a diary documenting everything that happens, including what you've done to try stopping it. This can help if you make a complaint. 

Get external information and advice, e.g. Lawstuff, the union representing your industry, the Human Rights and Equal Opportunity Commission (see below and links). These organisations can give you advice on your options and your rights. You can also ask them to act on your behalf if you don't feel comfortable doing so. They should also respect your confidentiality, though if you are concerned about this, ask them what their responsibilities are.

Tell someone. The person to talk to might be a Human Resource Manager, but if there isn't one you should report it directly to your employer, a supervisor/manager or health and safety representative (if your work has one).  This situation might be able to be resolved informally, without any official complaint being made. 

If the situation continues or is serious, you might need to make a formal (written) complaint that follows company policy. The person sexually harassing you might be officially warned, and be required to have counselling. If the sexual harassment continues, there might be a mediation process and, if all else fails, the person sexually harassing you might be fired. If you end up having to leave, you might be eligible for outstanding wages and entitlements. 

If the person doing the sexual harassing is your employer or they do not do anything to stop it, it's important you get outside support and advice. 
One last advice, whatever the situation you are in, let you yourself be responsible for it and do not ever let others to rule either the situation or your life, no matter whatever might be the reason...