22M with my 23F girlfriend of 3 years, I feel like I deserve better. Not enough attention towards me

So I've been in a semi-long distance relationship (less than 2 hours away) for the past couple of years. She's a traditional girl, isn't materialistic, faithful and very honest. She's been away for nursing school. At first everything was going smooth, we would see each other 1-3 days out of the week year-round. We would text/call one another during the day, enough to be filled in on each other's days. Although usually it was her doing much of the talking and I being the spectator. Which was fine with me for the most part.

Lately (past couple of weeks) she has not been as present in our relationship. She's found a new group of friends apparently and seems to give them all of her time. Now she will only send a few texts, call me for maybe 10 min a day only to quickly run back to her friends before saying goodbye. It feels as if she only feels obligated to keep in touch. Leaving me feeling like an option. I have called her out on it already (without appearing clingy/needy) but have not noticed too much action on her behalf. I've always been faithful to her and given her just the right amount of attention and affection, if not more than she deserved.

What bothers me is that I feel like I give more to her than she does to me. I give her the opportunity to travel all over the world with me on 7-12 day trips- 4-5 times a year. Having been all over Europe, New Zealand, Australia, Fiji, Hawaii,etc. All at 5 star resorts and hotels. In between all of this, I pay for meals, but her some clothing and nice things. I do these things out of love and wanting to share the experience with her. Never asking anything from her but her love and happiness.

She would constantly remind me of how lucky she was for having me. And she's right, I'm tall/attractive, independent, good sex, hold high morals, give value, nice cars, apartment, earn 500k+ and take very good care of myself. I say this with humility, even though you may think I'm a cocky prick. I genuinely feel like a man that is progressing every day and can bring much to the table. Crushing it at life! I know she can't reciprocate the same way, since she doesn't earn a whole lot of money. But I believe the least she could do is try her best to cater to my needs/desires and hold her promises.

I even pity myself at times for allowing myself to endure this. Even though she believes (or has believed) that I am the best thing to ever happen to her and anyone else would be a downgrade. As I have a line of girls who would take her place at the first opportunity. But I truly love this girl and want to be with her. Unfortunately it feels like she is taking me for granted and is seeking attention elsewhere. It really sucks...

tl;dr: I am probably out of my girlfriends league. Love her unconditionally with all my heart and pamper her like a queen. She hasn't been all about me at all recently.