Is being on symbicort (budesonide and formoterol) for asthma for 7 years but on off has bad effects and how can I stop using it without complications? I seldom get any attacks now

Bad effects? If you mean sore throats or throat infections, this is caused by the Budesonide in the symbicort (budesonide and formoterol) (a cortisone). This is common with inhaled cortisones. If you mean jittreriness, getting "hyper" or similar things, this is the formoterol (long acting beta agonists). Talk it over with your physician. Maybe you can be controlled with only the cortisone type spray alone.
See your doctor. If your asthma is well controlled, your physician may step down the therapy from symbicort (budesonide and formoterol) to another inhaler, but you should not stop it on your own.