Throbbing Sensation In Spine In Sync With Heartbeat. On Lexapro And Wellbutrin. No Issues With Thyroid. Thoughts?

Good evening!
I am a 29 year old BF. 280 lbs, 5' 4". I have a similar query as one posted on the webpage. I have been experiencing a throbbing sensation in my spine. It does seem to throb in sync with my heartbeat. It usually occurs when I have just sat down or when I am about to stand up. I have been on anti-depressants/anti-anxiety medications over the last 10 years. I have finally gotten to a wonderful cocktail of Lexapro 40 mg and Wellbutrin 150mg. (I am aware of being over the recommended dose for the former). My tests have shown that I do not have any issues with my thyroid, I do not drink alcohol nor do I smoke. I've experienced this throbbing for about 6 years or so, but it has been increasing over time- I may have the sensation 3-4 times per week. They last for several seconds to a minute. My reflex is to tighten up and freeze as movement makes the pain worse. My body does seem to get hot during this "attack", and I do not normally feel tense or anxious before as it usually occurs when I'm relaxed.