I am feel slight head pressure every morning in the sides and lower back of my head ,start feeling it late in the evening & early morning,it goes away after sometime. i took tylenol and advil for a few days thinking its head ache. is it sinus?

It is a headache as you describe it. You need to find out what is causing it which will help you get it under control. Not likely sinus from the limited info you give us. Discuss with your local Drs.

Generically, it is a headache issue, perhaps descriptive of tension cephalgia. Might ponder pain generator in neck or jaw, and even consider eustachian tube mechanisms, or dehydration. (?medication, recreational drugs, thyroid?) Based on post, hard to consider sinusitis, but ...seek help at your doctor's office with a full evaluation, as that should point to answer.