Please don't be offended by what I'm about to say and if I am wrong then I am sorry.
I agree with the others, it's far to open an ended question and I fear leads to reflect your level of experience. If you really have to ask what you need to take with you then maybe a four month trip is a little over ambitious for you.
Granted you haven't said anything about your camping location and if you plan to spend four months in a tent in your back garden then fine but if you are thinking of going off alone into the wilderness for four months and you need to ask what to take camping then you are an accident waiting to happen.
Sorry to be so blunt but better that than a poor SAR team having to spend weeks looking for you....or worse your body.
On a brighter note, there's sound advice from the other guys here, start doing lots of weekends and then weeks and build up...in no time you'll have a better idea of what you need and also what you can do and then you can safely go off alone for four months
I genuinly hope what I have said helps and doesn't offend you
Bam.