This may be a little off topic related to DhO forums, but have you had any experience working with chakras?
In answer to your question, yes, the sacral (Swadhisthana) chakra imbalances can appear as sensations like what you described, but even more relevant to the root (Muladhara) chakra. If you have any experience working with chakra centers, then it would be good to give particular attention to the three lower chakras (1st - Root, 2nd - sacral, and 3rd - solar plexus).
The PTSD that you mentioned is significant. Have you had counseling for this? Perhaps it would be good to find a Buddhist counselor who can assist you in processing through this trauma, as well as work with you as these things arise in your practice. Seriously, and with all honesty I think you should have some additional support (in addition to the helpful people here at DhO) from someone you can meet with regularly.
LovingKindness and Compassion