Don't know where else to post this but hear me out ...

I've been in this fetish for over 15 years now and I feel rather locked in by everything.
I have a girlfriend and I prefer pregnant porn over making love with her. I know the saying "make her pregnant then", but it's not that simple. 
We're still unmarried, schooling, and are in a financial abyss (mostly still paying for my graduate studies). And I've tried abstinence and it doesn't work.
It's almost as if I only prefer women that are pregnant and those aren't pregnant don't turn me on at all.

Even within pregnant porn, after spending tons of money on content, I don't even accept all content. I'm only into exceptional pregnant bodies, roleplay or the rare "pregnant goddess".
Anything below the 7th month of pregnancy doesn't even work anymore (it used to). Almost all camgirls sitting in front of a camera occasionally rubbing their bellies don't appeal to me anymore either. 

Perhaps I should seek therapy on this but it's such an awkward and embarrassing problem to share.
Does anyone share a similar experience? Do share!

Hello there, I feel as though you have answered your own question. If you are sexually unsatisfied with your partner now then where is the hope in moving forward without addressing the problem. You are not alone and you should know that. Not limited to this fetish either. Even though it is embarrassing I would seek some sort of professional help because I fear you're past the line of helping yourself out.
This has become the danger with the internet for people with porn addictions and the industry in general. Your desire is just a click away now creating an un-realistic world for real life. It will only get worse too. If your partner does not know about it yet I would discuss it first with her. Realize that she might blame herself as well for what you are going through. I would seek professional help first before laying it on the girlfriend. Know it is Okay to reach out.

It’s an addiction. Don’t over complicate it anymore than that. Recognize yourself as an addict and go from there. It’s sounds like you want to make a change. I’ve even it seems it for myself how your mindset starts to change after a few days of no porn. For me the challenge is my porn viewing is a part of my bedtime routine and my sleep suffers if I don’t. It’s all about strategy. Have you tried a new strategy to avoid looking at pregnant porn content. If you start to make progress, don’t log back in here to brag about that progress. Way too much temptation.

It is 100% OK to seek therapy. I think you want to, and just came here for that final push.

A therapist isn't going to judge you. Ask yourself if the momentary embarrassment from revealing this to a therapist is so much worse than having to live the way you're living right now. I bet it's not!

Get the help you're craving! You can do it.

Akhenaten is absolutely right. A therapist will not judge you and are absolutely bound to confidentiality. One of my buddies is a therapist who is very respected in his field. One of his areas of expertise is people with sexual issues. He doesn't discuss cases, but he is very matter-of-fact about the issues involved.

I've sought therapy myself (not with my buddy, of course) for matters related to divorce and severe illness. I brought up the fetish. These guys are totally chill about it. It's what they're trained for.

Can't hurt, might help. Go ahead!

Like what has already been said, too much of a good thing can be bad. All the porn I watch is pregnant, I’m not sure if regular porn can even do it for me anymore. In the past I have wondered if I could even get excited outside of this, and have tried abstaining. It sounds weird, but once I somehow managed to draw a line between fantasy and reality (like drawing a line in sand), pregnant porn being the fantasy, and reality being every day life and relationships. Just thinking in this way helped, or someone mentioning something like this to you can help, the brain is weird.

Otherwise you could see professional help, but something like this is not common where I’m from, so I understand the hesitation. Nothing wrong with it of course, it’s what they are there for.
It might be worth talking with your partner about it too, but make sure you are relaxed and calm before trying, don’t start off on the wrong foot and present your fetish as something weird or something that you have been trying to hide. I experienced the opposite, and it wasn’t much fun!

Just chiming in here: those who replied above me are all correct. You do need help, there is absolutely no shame in seeking it, and fuck everyone that has stigmatized mental health care in our society.

But honestly, I would try both 1) seeking some counseling, AND 2) abstinence from porn of any kind. I don't think you can hope that things will get better while you're still feeding the addiction. Kind of like how alcoholics can't "just have one drink".