I have had tendonitis in both forearms for 14 years. I also have weak joints to begin with. Mine will never go away and I am destined to develop carpal Tunnel if I am not careful. I have done the Physical Therapy route (which is the BEST), visited the chiropractor (also AWESOME), rested (like that happens with kids), worn splints, taken Tylenol, Valium, and a variety of other muscle relaxers. It subsides for a while, then returns after a bit if I do too much and if I am not in good fitness shape.
Start with making sure you are hydrated and eating well. Proper nutrition is VERY important. Check your posture. I found that I would kind of stoop when chasing after my two kids...once I saw that on video, I started making sure I walked straight and tall. Build a strong core with yoga, pilates, or other strength-training exercises. Everything is connected.
Do stretching exercises: http://www.youtube.com/watch?v=MXwfabQdcck&feature=re.... Use a heated wrap on the affected area before stretching, which will relax the muscles. One of my favorites is to sit in a chair, then let your arms dangle at your side, feeling your arms get longer and let your shoulders drop. Sometimes I hold a small amount of weight, which helps elongate those tendons.
Limit your time at the computer and check the monitor height and keyboard heights, as improper position encourage "hunching". Rest as much as possible and make sure that your activities are being performed properly. Don't "break" the wrist when doing activities, this causes your forearms to work harder.
I wish you the best of luck. With proper care, you can correct the problem.