Feeling defeated, what should I do next? (Second attempt 550)

Hey guys, I need your advice. Yesterday was my second attempt at the GMAT and I failed.

Background: I started my preparation back in November 2019. I needed a decent GMAT score (anything above 600) to apply to a Msc in my dream school. I bought the OG guide 2020 thinking that was enough for me (oh boy I was wrong ). I didn't understand the majority of topics tested but I haven't any idea about how to properly prepare for the exam (I didn't know there were prep options available ). Anyway, I found out about GmatClub just before my first attempt in January. I started looking for prep options and I went for "Foundations of Math" and the complete MGMAT guides. In the mean time, I decided to take my scheduled exam anyway as I couldn't postpone it anymore. As you can imagine it was a disaster, I scored a poor 440 (Q17, V32) on the real exam.

Fortunately, I was very motivated and that horrible score only encouraged me to do better. This time I studied for 4 solid months. I had a lot of time to dedicate and I studied for 4-5 hours everyday (after that I start to lose focus). I first covered my basics with Foundation of Math for a solid month doing all the drills multiple times. Then, I went through each of the guide front to cover. I tried to make sure that I was comfortable with a topic before moving on the next one (I did the exercises on the OG according to the topic I just covered using the timer of GMATClub to keep track of my responses and timing). After I completed the majority of the books for quant I took a CAT: 510. Finally, I started to see some results and the progress that I was making. I found the MGMAT guides very useful and easy to follow.
I list my GMATprep CAT's results:
610 (37Q, 37V)
630 (41Q, 35V)
600 (40Q, 32V)
620 (43Q, 33V) - two days before the actual GMAT.

The day before the exam I only did a light review of my notes and some exercises, nothing crazy. I went to sleep early and it was all good. In the morning of my exam the anxiety kicked in as I knew this attempt was my last shot before having to wait a whole year to attend a Msc at my dream school. Anyway, I went in, confident to get a score around 600. I started my exam with quant. For 2/3 of the section the questions asked were similar to those I usually solved at home (I got one probability and one combination question).
The last questions (~10) were very easy (fractions and very basic DS question), so I knew something went horribly wrong. Verbal was normal.

I ended up with 550 (Q32, V34). I couldn't believe my eyes.

Needless to say, now I'm kind of lost. I need to wait this fall round of selections to apply again and hope to have a 600 score by then. I'm not sure if I should try again with MGMAT guides or what. Also, I almost run out of OG questions. I still have a lot of time to dedicate to prep, and I would like to give me another 2-3 months of serious studying. I feel demotivated now, but I really don't want to give up. What should I do?