Brother, I'm in similar shoes to yours and have had thoughts and feelings very similar to yours in the past. I think Satan is always trying to bring us down with bitter thoughts of what we don't have. I think especially when you are single it is very easy to get into a chronic mindset of feeling as though you're lacking. And then it's easy to blame yourself for that and become really depressed about it.
I was a bigger kid growing up once I got past age 5 or so, and looking back it seems like I heard the message from everywhere in my life that there was something wrong with me because of it, or that I was somehow a second rate human being. Kids at church called me jelly belly, kids at school (and one bully in particular) made fun of me--even my grandparents, who completely meant well and prayed over their entire family almost every day, would pray in front of me that members of my immediate family would lose weight. And, of course, anytime you're a big brother with two little sisters, big brother is gross (they still say things to that effect sometimes). I internalized all of this and without really saying it out loud, I came to the conclusion deep down that I'm a second rate human being because I'm not skinny. I have always thought that when people look at me, that's what they see, so there's no chance that a woman would ever love me. How could any woman want me when there are so many better, skinny options out there?
I still get emotional typing this out because these are such deeply rooted lies that I've believed for so long. I went through a period in college where I lost a bunch of weight and was living a pretty healthy lifestyle, but those beliefs still existed. I look back at pictures from college and realize that I looked totally fine, but I didn't feel that way at all at the time. And after I graduated college, you could say that all of those lies became a self-fulfilling prophecy. Since I mainly saw myself as this unattractive, overweight guy, my habits and attitude began to reflect that and I gained a lot of weight. I'm now in a recovery process, you could say, trying to develop healthy habits.
Looking back on those pictures of myself in college and thinking about how poorly I felt about myself even then caused me to realize that something is wrong with the way I see myself and that I am always going to believe those things about myself no matter what my weight is unless something changes. Through a close-knit Bible study I've been a part of for the past year I've had the opportunity to expose some of these lies and begin to combat them with truth.
The reality is that I am not a second rate human being because of my size, physical shape or ability, self-control, or anything else, and you aren't either. You are a valuable, important, and loved human being with impassable worth because you were created by God and fought for by God even unto death. We don't have to chase after acceptance from anyone because we already have it in the most perfect way in God. You could ask 1,000 women about their opinions on your physical appearance or mine, and you're going to get opinions across the board, and some of them could feel differently in a year or even a week. Human opinion is fleeting and often selfish, but God's opinion is inherently loving and selfless, and most importantly, it's the truth. No one can tell you that you aren't worth cherishing because God has already told you that you are. Before you try to do anything else, you have to believe and internalize this. Everyone has something they dislike about themselves, but God loves all of it. His image is in you. With that foundation, you can escape those feelings of lacking. You can stop feeling like you need a marriage to complete you and affirm that you really are worth loving because you are already complete in who God has created you to be and you are already deeply and powerfully loved. You can feel free to live a life of joy and health to His glory and not to try to impress somebody else. And if God would bring a woman into your life, you would be free to love her as a girlfriend/wife rather than as a god.
Now I can't say that I'm there yet. The lies are still there and still try to bring me down, but that freedom, that health, that closeness with God, and that joy are things that I'm pursuing, and I would encourage you to do the same, brother. You will probably fall down at times as I have, but commit now to getting back up again and pressing on. You won't regret it.