While not common, jaw clenching, grinding of teeth and a general condition known as bruxism CAN be caused by some of the medications you are taking including citalopram, trazodone and Wellbutrin. It is most commonly associated with the SSRI (selective serotonin reuptake inhibitor) you are taking, Celexa. 

Bruxism is characterized by clenching, grinding of the teeth and difficulty opening and closing the jaw. It most often occurs during sleep, but can really occur at any time of day. Bruxism may also present with complaints of headache, pain in the jaw muscles, decreased range of motion in the jaw, and dental problems indicative of tooth damage. Over time, studies have shown that there is clear evidence that SSRIs are associated bruxism. The incidence of the side effect appears to be fairly rare at less than 1% of patients experiencing it.

Multiple studies have described the SSRI side effect of bruxism. Most people started having symptoms within the first few weeks of SSRI therapy and patients gained relief after the dose of the offending SSRI was decreased. Studies suggest that SSRI-induced increase in serotonin acted to reduce dopamine levels in areas of the brain where it acts to inhibit certain movements including bruxism.  They theorize that SSRIs increase serotonin in the mesocortical tract, which inhibits the release of dopamine. In this tract dopamine acts to inhibit motor activity including that for jaw muscles. Reducing dopamine levels would thus reduce this inhibitory effect and allow the development of bruxism.

As I mentioned, patients responded to a decrease in SSRI dose. They also seemed to respond to the addition of a drug known as Buspar (buspirone).

It is odd thought that the drug Wellbutrin (which you are also taking) acts to INCREASE dopamine. Even though it increases dopamine, bruxism is a listed side effect of Wellbutrin as well. 

It's always tough to exactly pin down why side effects are happening but there is a good chance your problems may be stemming from some of the medications you are taking.