Is it possible for chlamydia to come back on its own even though i was cleared of it 2 years ago when i was pregnant with my son?

Not really: If you were treated with the normal protocol of meds 2 years ago the infection would clear. Some actually do a test to confirm this weeks or months after treatment. Although it may be upsetting I would consider any new infection from a new exposure, not a hibernating germ that was not cleared the 1st time. Either way, your contact needs to be treated when you are.