Is it possible for someone who has no record to get 7 years on an aggravated charge with no evidence supporting it?

anything is possible with a bad attorney.  you can be squeaky clean and get charged with murder. it's up to your attorney to try and minimize the punishment or show that it never happened.  and yes, they can prove your case through circumstantial evidence.  

It is possible, and the main reason is how Texas courts treat evidence. A conviction can rest on the testimony of one witness, including the complaining witness, if the jury believes that person. Witnesses who were not there for the event can still testify to what they saw afterward, such as injuries, the medical response, or what someone told them right after. Having no record does not rule out prison, and seven years is within the punishment range for many aggravated offenses.

An appeal does not retry the case. It asks a higher court to decide whether legal mistakes happened at trial and whether the evidence was enough for a reasonable jury to convict. The deadlines are short. In Texas, a notice of appeal is generally due 30 days after sentencing, and a motion for new trial has the same 30 day window. If those deadlines have passed, other tools exist, such as a writ of habeas corpus, but they are harder.

A criminal appeals lawyer can read the trial record and tell you whether there is an issue. The record matters more than how the case felt in the courtroom.