How heavy is your
Nano Ti Tornado racquet? I found some specs for a Head Ti Tornado racuet but I am not sure if it has the same specs as the Nano version that you have. (Not certain if the following link for the Tennis Depot will work)
http://www.tennis-depot.com/head-ti-tornado-16-19-tennis-racquet
This page shows that the Ti Tornado (with strings) weighs about 10.5 oz which is a little bit less than 300 grams. It also indicates that it is slightly head-light (almost evenly-balanced) unstrung. With strings, it is probably somewhat head-heavy. If your racquet specs are close to this, then it is
not really very heavy at all. A cheap racquet like this one might have a lot of variation in its specs -- your racquet might actually weigh a lot more or a lot less than the published specs
If you have a long fast swing, you probably don't really want to hit with a strung weight that is less than 300 grams. If you hit hard or play with other people who hit hard, then a lighter racquet may not be good for you at all. However, if you have short to medium swing lengths and slow/medium swing speeds, a lighter frame may be ok for you unless you are playing with heavy hitters.
It might be that your racquet has a balance that is too head-heavy for you. It also might be a frame that is delivering too much frame shock to your arm.
Or is could be that you are using your arm too much to generate swing speed. You should be using your legs (with a knee bend), hip rotation and upper body rotation on both your groundstrokes and your serves. If you are not bending your knees and using body rotations, then you may be putting too much stress on your arm and shoulder.
The
Volkl V1 Classic is a racquet that is one of the most arm-friendly (and shoulder-friendly) racquets available on the market. It has a very soft feel and delivers very little frame shock to the arm/shoulder. It is a head-light frame and weighs only about 308 grams (strung).
http://www.tennis-warehouse.com/Volkl_V1_Classic_Midplus/descpageRCVOLKL-VCVN1.html