You can easily test it yourself with a simple clip on IP gauge. They are inexpensive and will quickly determine if you do have an IP problem. Here is an example http://www.piranhadivemfg.com/item/Standard-Middle-Pressure-Gauge-3129 There are several things that can cause an unstable IP, way to much to go into here but if you check it, you will at least have some idea of what the problem is.
I just bought that. I think I should have it so I can check it anytime I have some service done on it. Thank you.