At your stage, 3 months with 1-2 times per week of diving, I wouldn't even look at RV or even FRC diving at this point. That would put you in a position to squeeze more than it would help your dive response. The amount of diving you are doing would be enough to strengthen the dive response and allow for adaptation to the depths you are achieving.
You said you were comfortable around 22-28m and that your PB was 34. What it seems like is that in some part of the equalization process you are, without realizing, using you diaphragm and as you approach your RV at around 30(ish)m thats when it starts to get uncomfortable because you are working harder and harder to get air out of your lungs.
The best thing that you could do would be to take a small step back in depth, hang the line at around 25m and just work on repeating that depth multiple times over a session. While doing that you should bring awareness to your breathing muscles and try and feel exactly where the equalizations are coming from; Mouth, Chest, belly.. Once you master 25m and can do each dive with perfect equalization using Frenzel, or Mouthfill, then you can use those skills to move the line deeper and work the same things at 30m, 35m and so on..
Its hard to do when you want to go deeper, but sometimes a small step back to an easier depth where you can practice skills will help you progress faster and deeper in the long run. If you master the skill of a perfectly relaxed frenzel, you could quite easily make it down to 40-50m without any real problems.