Hi vbphelps,
Saving your work as an mp3 and then returning to edit it later is not a good workflow and will result in the quality of your file decreasing every time you save it - this may be the cause of the problem you are describing.
You should always try to store your original files in a lossless format like FLAC or wav. Here is an example of what I believe to be a good workflow:
1. Make a recording the same way you are doing now.
2. Save your recording as myrec.wav
3. Make any edits you want on the file
4. Save your edited file as myrec_1.wav
5. Now save an mp3 version so you have your recording in a small useful format --> myrec_1.mp3
Now, let's say you decide you need to make some changes to the recording:
1. Open the file myrec_1.wav
2. Make your changes
3. Save the file as myrec_2.wav
4. Now make an mp3 version --> myrec_2.mp3
With this workflow, your mp3 files will always have consistent quality compared with each other and you will also have some historical back-ups you can use if you need.
Regards,
Ben