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 obtain a history from you and examine you, I can not comment on a formal diagnosis or treatment plan for your symptoms. However, I will try to provide you with some information regarding this matter.
Trouble with memory, as you mention with word finding and recall, in younger people is uncommon, but there are causes. One such cause is from hypothyroidism (i.e., low thyroid function). This condition can cause fatigue, weight gain, cold intolerance, constipation, and memory/concentration problems in addition to several other symptoms. Another possibility that can cause some of your symptoms is anemia, which can cause severe fatigue and trouble with thinking. In addition, other causes include certain vitamin deficiencies. These can all be diagnosed with simple blood tests. You do mention that you are depressed and anxious. Both of which can cause some of the same symptoms and improve with appropriate treatment. Finally, certain people live into adulthood with thinking troubles only later to be diagnosed as learning disabilities or attention deficit disorder (ADD). Many people think of this as a childhood disorder but it can start in childhood and not be diagnosed until adulthood.
Regarding your thunderclap headaches, you should have these evaluated if you have not done so already. Thunderclap headaches can occur, but they are worrisome in that they have similar qualities as subarachnoid hemorrhages (i.e., bleeding in the brain). These are typically described as the worst headache of ones life and may also have associated neck stiffness. Subarachnoid hemorrhages are diagnosed by a scan called CT and also with lumbar puncture. I’m not saying you have a subarachnoid hemorrhage but anyone with a thunderclap headache will have this in their differential of diagnoses. I am glad that you have had an MRI that was “clear” as you state. Hopefully, an MRA was performed along with the MRI to examine the vessels.
There are several potentially treatable causes to your symptoms. I strongly suggest you continue sharing your concerns with your physician. She/he after examining you and obtaining a history may choose to recommend referral to a specialist as necessary, but also may do basic laboratory work to rule out the treatable causes.
Thank you for using the forum, I hope you find this information useful, good luck.