Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your symptoms is. However I will try to provide you with some useful information.
The pressure and pulsating feelings in your head, if they occur in episodes, may be migraines. Typically, migraine headaches cause a pounding sensation associated with light and sound sensitivity, nausea. In your age group, tension type headaches are common as well. However, there are other causes of headaches/head pressure, and imaging of the brain (for example with a CT scan) would be indicated to exclude a tumor, vascular malformation, or some other secondary cause of headache. If you have already had brain imaging and no abnormality was found, and if your physician diagnosis migraine headaches or some other primary headache disorder, there are specific medications that can be prescribed and can be very effective in most headache disorders.
In someone your age, neurodegenerative disorders such as dementia are extremely rare, and a genetic or metabolic disorder that causes cognitive problems in young adults would be associated with other neurologic features. Memory problems at your age most commonly could be due to a metabolic disorder such as thyroid problems, anemia, sleep disorders (obstructive sleep apnea can occur in young people particularly if they are overweight or snore), and other systemic problems. Memory symptoms/poor attention and recall can also be a manifestation of depression, which is a serious medical condition that should be treated and can successfully be treated. In young adults such as your self, attention deficit disorder (ADD) may also be the cause of inattention and subsequent inability to register information well and later recall it.
As you can see there are many potential causes to your symptoms. Re-evaluation by a general physician/internist is recommended, with referral to a neurologist (or another specialist) as indicated.
Thank you for using the forum, I hope you find this information useful, good luck.