The stretching does sound like gas, yes. At least, it is worth addressing to see if that might be the issue.
First, you have to get that burp out. It's very important. Keep patting her back and then frequently changing her position and resume patting. It might take ten minutes, but it has to be done. Sometimes if you swing her onto her back and then back onto your shoulder, that change in position brings it up.
Second, you could try a little gripe water in the bottle. It is herbal (not a drug) and worked very well for our DD. We used it in, I think, every other bottle for probably 3-4 weeks, and although it did not stop the gas completely, it seriously reduced it to the point that DD was no longer uncomfortable.
Third, if you are using formula, you could try switching brands. I do not mean switching from regular to soy, for example, but rather switching from, say, Similac to Enfamil, using the same formulation you were before. So if you are using regular, iron-fortified Similac, try switching to regular, iron-fortified Enfamil or Gerber. You can switch cold turkey with no issues. They all taste slightly different, so DD might think that is weird, but one might be better for her for gas than the other. With our DD, we switched from Enfamil to Similac, and along with the gripe water, her gas was seriously improved.