Patience. Easier said than done.
Your work is very good. Perhaps not great, but thoughtfully assembled, crafted and communicated. Landing that dream position anywhere is very tough for a majority of graduates. Most of the high end firms look for very specific skill sets where graduates can plug in directly. I found they don’t look for a good fit, but a perfect fit. That shouldn’t discourage you to apply, but help cope with understanding why some firms hire who they do. This goes nothing against your character or your work. There are a wealth of folks in your place and to the like, there is a wealth of answers to this question that has been answered on this forum many times over.
Months of application is not uncommon. It took myself, and I’m sure many others, years to get into a choice design position, knowing we had the drive, skill, and aptitude “if only someone would give me the chance”. But growth is about time, perseverance, maturity, and to a certain degree, luck.
Economically, as a designer, you have to be where you are needed/demanded. Not to say that where you are isn’t in demand, but you may have to hedge your bets a little if you want to grow into the designer you want to become. That also goes to say that your salary will also go against the volume of talent within the area that can do exactly, if not, better than what you can do.
Talking to professors is great, comforting, and rewarding. But they already taught you all you need to know to be a designer. Find a mentor, one NOT in design and try to build a foundation of communicating SIMPLY what you do, and can do. This practice will come in handy when your selling design to non-design executives and peers. Handing over a portfolio is great but not everyone will get it or understand on the first read. You’re graphic comps are great so keep it up!
Lastly, have the confidence that you’ll get there. You will, I promise. It’s an arduous road, full of disappointment, joy, reward, conflict, frustration, and the most important Ego. This is an uphill journey that you and only you will pave. Eventually, you’ll have to do all of this, and at the same time, fall in love, raise a family, and give hope to others on the journey. And when you get there, pass on the advice to others who were once in your boat. Good Luck.