Im not terribly smart. how can i improve my academic achievements?

im 20. i was adopted at 12 from another country. i was about 2-3 years behind kids my age, regardless my adoptive parents put me in 6th grade. i learned english in a spam of 6 months. however ive always struggled with school. i dont have any mental issues such as add or dyslexia, but i have a negative view on my intellect. ive always been behind and it shut down my ego. now im in community college. i flunked my first year and im academic probation. i decided to take a year off. this will be my 2nd semester off and im just working. however im determined to major in biomedical engineering. i know for me thats an almost impossible goal but i need advice. how do i catch up with everyone. how do i find the determination? are there any books on study skills? please help.