How can I conquer social phobia at 30 yrs old already?

You are young!!! Get help. See a psychotherapist who works with social phobia and see a psychiatrist. There are medicines that can help!
Psychodynamic tx. Find a psychodynamically oriented therapist to speak with about work anxiety. Usually work anxiety is not just about being at a job. Other factors often contribute Then, if needed, go with a psychiatric referral from your GP. GP's can prescribe psychotropic meds for anxiety and depression, but they do not have the specialty training that psychiatrists do.
Exposure, Gradual. Most effective therapy =systematic desensitization. Involves facing/exposing yourself 2 feared object/situation but gradually, in progressive steps- from a situation assoc w/ mild level of soc anxiety 4 u, up 2 one assoc w/ extreme level. At each step u experience fear but u "stay w/ it" until level drops/u feel relaxed. Work w/ behavioral/cognitive-behavioral specialist esp. Clinical psychologist.
Not too late at all. Another way to look at it is you still have so many good years ahead of you. How can you not try to conquer it? Also, more and better treatments have been increasingly available. If you are suffering, now is a good time to see a psychiatrist. You may want to consider taking medication.
Social phobia. Behavior modification helps, such as exposure with response prevention, imagery, etc. Need therapist to help.