I know how you feel, I have been in your position before. For my first SAT, my reading/grammar score was a 520, which stressed me out because I was a straight A student, and usually did good in english class.
Lucky for you, the grammar section is arguably the easiest section to improve on. After only a few hours of reading and memorizing grammar rules, I went from getting 10+ questions from to only getting 1 or 2 wrong. I know that you only mentioned struggling in reading, but if you get your grammar score up, then you can afford to struggle a little bit in the reading.
While improving on the reading section is more difficult than improving on the grammar section, it is still very possible. The most important thing that I did to improve my reading score was changing my mindset. Instead of giving up after a hard question, I told myself “the answer is somewhere in the text, I just have to find it.” that, along with doing many practice tests, helped me improve my score by a significant amount.