Your speeding ticket will not be expunged from the court record. Supervision is not legally considered to be a conviction, but a court record still exists and continues to exist even after the supervision is completed.
As to seeking another supervision or hiring a lawyer, that will be up to you. If you make a bad decision on your own, you will only have yourself to blame. With that said, in many cases, supervision for a speeding ticket is a good result. I can't say whether supervision would be good in your case because I don't know enough about it.