If you qualify for an expungment, you can do it on your own. An attorney is recommended, but not required.
Whether you qualify, depends on the precise resolution of your case and whether you were actually convicted or whether you had a deferred adjudication. Here is a link that describes the types of outcomes that can be expunged:
Based on your description, it is likely that you were convicted and don't qualify for expungment, unfortunately. But, as I said, it depends on the specifics of your case and it is worth paying a local attorney (in the location where you were sentenced) a couple hundred dollars to do a detailed review of your case file.
If you don't qualify for expungment, a pardon can help. Here is a link that describes this process:
Please let me know, if you have follow-up questions.