Mild Acne on back different types of acne??

I am an 18 year old male and have had Acne on my back for about 2-3 years. I Left it for a while but last year I started on Oxytetracycline. My acne on my face cleared up  and so did my back. I found that sun bathing and going in the sauna at the gym helped get me clear.

As i entered winter of 2010 the spots came back and Oxtetracycline lost its effect. I recently quit the medication due to it no longer having an effect, also I do not like taking medications due to the effect and harm on the body.

I stopped going to the gym and using the sauna and the acne on my back became pretty bad. I then started using Sudacrem on my back which helped alot and I started using the sauna again. I havent got completely clean but it sure helped. Due to exams and coursework, gym progress stopped once again and the acne on my back got worse too.

Im hoping to grow out of it, probably the wrong way i know but I refuse to take medication. I have started to notice that my back is very dry so I am using baby lotion after a showe to see if moisturising helps.

Now on to my question..
Aside from the pain and blood stained t shirts, there is one spot which I have had for about 2 weeks. It is like a blister, soft but painless. It feels like it has watery fluid in it but I dared squeeze it. It scabs up then the scab will come off again, due to me picking it and clothes catching. I have put Sudacrem on it and it has seemed to make it smaller but it is still there and ever so hard to leave alone so I do think some of it is my own fault.

Is it just a type of acne spot or is it something more serious? I am  massive hypercondriac, stress plays a big part of my life whether i know it or not and I am very self concious which I think has played a part in my acne.

any answers?

Much Appreciated,

James.