Any ideas how I can get rid of this? It isn't pain per say, but it is constant and is in the area right below the iliac crest on both sides of my butt. It seems like a muscular tightness in the hip extensors and it always gets aggravated after any leg day. Any useful stretches?

Thanks,
Josh

Do you experience numbness down your leg as well? That might indicate sciatica.

Anyways the pain you report seems to match up with this:

from sarapin.com

liolumbar Syndrome: A Commonly Unrecognized Cause of Sciatica
Iliolumbar syndrome-- also known as lumbosacral sprain--is a frequently unrecognized cause of sciatica that results from inflammation, sprain, or tear of the iliolumbar ligament. This ligament bridges the transverse process of the fifth lumbar vertebra and iliac crest(Fig. 5 (http://www.sarapin.com/fig.html#5)). People who lift heavy objects while rotating the back--lifting crates off a truck for example-- are especially prone to the iliolumbar syndrome.
Diagnosis: Patients complain of pain that varies from a constant, dull ache aggravated by activity to extreme severity. Pain is usually localized to the posterior portion of one or the both iliac crests (patients can often point to the precise site), but may spread across iliolumbar region.
A careful musculoskeletal examination usually illicits the pathognomonic signs of iliiolumbar syndrome. The most typical sign is tenderness of palpation of the posterior iliac crest on the involved side. Patients frequently have a discrepancy in leg length 1.5 cm or more, and pain and sciatica are more pronounced on the side of the longer leg16 (http://www.sarapin.com/ref.html). Increasing pain with lateral bending away from the involved side is the characteristic sign of ilio lumbar syndrome.17 (http://www.sarapin.com/ref.html) Patients report pain in the iliac crest or directly below on straight-leg raising. To distinguish this pain from that associated with disk herniation, the physician should flex one of the patient's hips (with the knee also flexed) through its full range while holding the opposite leg down on the table. If this maneuver causes back pain on the involved side, the test is positive. (In the root compression syndrome, it causes only minimal discomfort, or even relief, since the sciatic nerve is relaxed and exerts less pull on the nerve root).17 (http://www.sarapin.com/ref.html) Neurological examination is normal in patients with iliolumbar syndrome.

Pretty technical. I might see a doctor to rule anything out. Suggest massage and some stretching exercises. This is a great site for stretches, and exercises come to mention it. http://www.exrx.net/Lists/ExList/HipsWt.html#anchor169231
The heavy lifting is probably the cause.