Almost every time I try to astral project something pushes me back into my body. The few times that this does not happen I either have gotten too scared to astral project or I sense that it is a bad idea to do so. The most recent attempt ended when I was almost out but I saw this thing trying to choke my body so I immediately stopped. The only time that I was able to astral project was during my surgery or when I was in danger (like about to fall on my head) but those were more like an OBE.  

Also, when I try a method it usually almost works and then when I try it again, it does not even come close to working. I have had a few encounters where it felt as if something is trying to push me out or take control of my body.

So, is something trying to protect me by pushing me back in my body? Am I in danger and if I am, why? Has anybody else had these problems?

You're fine.  As the above has posted, "Don't fear it, embrace it."  I've been through this before.  As I was projecting about five feet above my body, I felt this intense fear of the unknown and saw an evil entity in my minds eye.  A few seconds later, I was pushed right back into my body.  

There are negative entities out there that do not want you to project.  They will mess with you because by default they know that you are afraid.  They rely on the ignorance of your own true power.  Don't play into their pesky games.  You need to remember and believe that you are so much more powerful than them.  

http://www.youtube.com/watch?v=LMCpcgOSTJw

^ This man's name is Rich and he has been helping the public experience astral projection.  I suggest watching his videos (he has a huge variety) as his vast wisdom will help you.