Hi. It does sound like you are getting tension headaches rather than migraines. Posture exercises, breathing exercises and exercise should help you a lot. Their is a book that I recommend. The name is "Mind over Back Pain." Even though the title refers to back pain, the subject is TMS. A syndrome for holding tension in the body and manifest mostly in the back and neck/shoulders. It certainly can't hurt to check it out.
Hope you feel better soon!