Part of ridding your life of demons is learning to face your own "demons". That is, identifying and confronting the things in your life that are negatively out of balance. It starts with something as simple as cleaning your house - it is well known that messy or dirty surroundings attract negativity and by extension evil. If you are lazy, exercise. If you are overweight, go on a diet. If your boyfriend abuses you, leave him. I know this doesn't sound like great demon-fighting advice, but it is, in fact, the best advice you're likely to get. It's much harder to clean up your mind when your surroundings are a mess. As you go through and sort out your thoughts, go through and sort out the rest of your life as well. It doesn't have to be overwhelming - that's another thought that can simply be challenged and changed.
As physics will tell you, momentum is a great way to sustain the direction of energy, so start making positive changes RIGHT NOW and build on them - a little every day. Ignore the negative things in your life and they will go away. Choose positivity in everything you do and soon you will be nothing but positive energy.
The best way to start is by literally cleaning up your surroundings. If you are disorganized, start finding places for things to be, if you need to vacuum the floors, do it now. A messy life is a huge cause of stress, which is negative energy, which invites in more negative energy, which is like leaving food out for any malevolent spirits around.
If you feel overwhelmed, just pick one thing to clean up a day, one habit to start working on. Every little bit will make you stronger and the culmination of your efforts will show you how powerful you really are. You may not need an exorcist after all. You may be able to create enough positive change that the demons will starve and like any beast, will soon go find somewhere else to feed.
With enough practice demons will have no interest in you anymore.