OK Elva. Straight away I am going to use a term psychosomatic. That is to say your brain's perception of reality is not happy. So, it is using your limited anatomical/psysiological/neuralogical knowledge to really describe that it is unhappy, In fact, it is more than unhappy...it is fearful. Other emotions that are available for you are sad, anxious, guilty, inferior, lonely, embarrassed, hopeless, frustrated, angry, overwhelmed. The over-all dis-ease summary are internalized to your body in somatic (symptom) forms...I feel pressure inside my head. What I really think is reflexively happening is that you have a significant stress level internalized which translates to increased catecholamines, which in surges causes your heart to surge in pressure, which you feel as pulsating and pressure. The brain, itself, has no pressure Gage sensors. Significant over pressure within the skull is felt by headache. The keys words here are, "...whenever I feel stressed?"
If I am correct then, you might want to ask what can you do to relieve your distress. First thing for me to say that is just the most appropriate real thing to say is life has two perspectives; good and bad. Yes, when we feel like we are up against a wall and looking for a way out it is not easy to admit that the absence of any part of our life would be the answer either.
Yes, absolutely, there is self-help for you. The bottom line issues for you is HOPE and DETERMINATION. These issues are either there or they aren't. The best way to start is to be drug free. From that starting point then there are two ways to approach this anxiety-depression issue that we as human all have to deal with. you can go to a doc and get some Xanex and Paxil, etc (I don't have time...I'll pay the doc and buy the meds. Just get it over with). Or you can really go the self-help route by first, not isolating yourself. Good mental health is always supported by good community. If you want to learn how to ski then don't ski with the beginners. Then there are corrective activities. Other activities that promote that happy mood chemical in the brain. Exercise itself is very positive on the effect of the brain in so many ways. Eating well and balanced. I know that you are going to school and probably have three girl friends and three jobs, but I want to give you more homework. I encourage you to invest in two books; David D. Burns, M.D When Panic Attacks, The new, drug-free anxiety therapy that can change your life. and Michael Shermer's Why People Believe Weird Things.
There is work to be done, but if you are successful now, you have a lifetime equivalent of a Doctorate in Psychiatry. I wish you well.