Nemanja, I think that my situation concerning jelqing is close to yours. When I first tried jelqing, I had got the technique from a pay site (I got it for free but still it came from there). This technique said I had to be erect to jelq. At this time, I was having a little bit of ED issues (I had trouble getting very hard without stimulating myself to the point where ejaculation was inevitable). So I tried jelqing this way for a few weeks with very bad results. No gains and even worst, my problem of being unable to achieve a fairly good erection without a lot of stimulation got worst. So I stopped PEing for about a month.
Then I found Thunder’s and decided to give another shot at PE. This time though, I tried an other approach to jelqing: no extra stimulation. I just start with a flaccid dick (very flaccid since I do stretches before jelqs) jelq without any expectation regarding the erection level I reach. I just jelq and kegel to try to pump up my dick gradually. If it gets pretty hard, all right, if it stays soft, all right too. I jelq for half an hour this ways, changing speed and the positioning of my hands. I often jelq almost totally flaccid (except that I get some pump from jelqing). For me this was the solution. I gained both length and girth and better than that, I improved my “erectile/ejaculatory” condition a lot. Now I have a bigger dick, I’m harder, I last longer…in other words, I’m happier.
All this to say that jelqing at low levels of erection CAN MAKE YOU GAIN both length and girth.