Correct meditation Technique

I am subject to thoughts containing anger, hatred, resentment etc. which causes me lower back pain. I am using medicines but useless because the relief is temporary. I am a meditator but I watch breath at nose tip, which causes me more tension after the session is over by 2 -3 hours. I have read somewhere that watching breath at belly i.e. Dantian is also recommended. I have tried it once and found it more relaxing. What should I do? Watch breath at nose tip or belly button? I have been doing nose tip meditation for six months which took me sometimes to thoughtless awareness - but did not solve my problems of physical pain and irritability