anal..

I understand this isn't everyone cup of tea so if this disturbs you please do not read. 
Myself and my partner have started to do anal. At first I didn't like it cause it just plain hurt but than it started to feel kinda good. 
It's just afterwards that worries me at the moment. 
I need some help I'm not sure what anal can do if not done properly or what problems it can cause in my system. There is no information that I can find and I'm not trusting the internet. I just would like to know what is the best healthy and safe way for us to do it and what not to do.