Will combining tramadol with seroquel, (quetiapine) trazadone, and doxepin increase my chance of getting serotonin syndrome? 400 mg of tramadol.

Yes. Tramadol can theoretically increase the risk of serotonin syndrome when combined with doxepin, and/or trazodone, and 400 mg is not a small dose. Whether this would happen with you is impossible to say; you would need to carefully discuss risk vs. Benefit with your prescriber.