what should be the minimum number of weeks between each prp sittings for hair loss for a total of 6 sittings???

Most doctor space out PRP treatments every few months. See your doctor and their specific recommendations.  There are no set "rule".

Hello,
For my patients ı suggest to get the prp treatment done every 2-3 months. Other doctors can tell different time period

At present, nobody can tell you the precise answer. There is no general agreement in the world yet on the ideal spacing of PRP. We follow a pretty well accepted protocol of PRP sessions every 3 months for the first 2 sessions and them every 6 months. In the largest published research study to date, this was the way PRP was administered as well. 40 % of study participants had significant improvement. Other methods include monthly for 2 or 3 times and then spaced out more after that. That's not how we do it but no study has yet to show the optimal spacing of PRP treatments, or the optimal setting or the optimal machine to use. We still have a ways to go to understand how to best deliver PRP!