When one's entire identity revolves around a kink, it can be seen as a turn off to people. I'm not talking about a sexual turn off either. They may see you, as a person, as being singularly minded and obsessive and that raises red flags in their minds. Your compromises don't work, because you make your partners feel like a repository for your sexual frustrations or obsessions. No matter what the compromise, how little you mitigate it as a major factor, I'm sure you still have an intense focus on it to a degree that can make another person uncomfortable. Even if you try not to write it as much on the page or mention it during planning, they still look over and see that they're planning or writing with "impreg21". Consider someone that likes to play domestic abuse, and they fashion themselves with the username "bitchhitter21". You can see how that might raise some eyebrows even when they swear they won't add much domestic abuse to their role-play and will TOTALLY respect women. When you also factor in the gender thing, as has been already discussed, you paint a picture for people that will wane tolerances rather quickly. If you do indeed seek to only play with women, and have only conversed with women (highly doubtful, some of the women you've likely played with are men), then that just compounds those red flags in their mind.
Why does he only play with women?
Well you answered it here. You're concerned with whether or not someone is getting off to your writing. Regardless of whether or not you intend for them to do so, that's the image of yourself that you put forth. You signal to people, whether you intend to or not, that your sole intent isn't actually to role-play. You're looking for a shared sexual experience with another person. It makes people feel as though you aren't here to write a story with them. You're just here to cyber-fuck them with the thin veil of a pretense that you're "role-playing". To them it might meant that this creative exercise, with some catharsis attached, is now suddenly a seedy meeting in a glory hole with a strange man. That idea might be fun in role-play, but I assure you most women don't want to feel as if that's the reality they've been thrust into when they believe themselves to be in a safe place.
Furthermore you have made it known that you aren't actually interested in "non-erotic roleplay". This reads as if you're just here for the sexual gratification. Unless you are adept at masking this intent, this is going to going to come off as distasteful. Believe it or not, many of the women on this site (those that actually are) aren't exactly virtual succubi with the sole desire to get on here and fulfill sexual fantasies. I'm not saying you specifically view anyone in this manner, but you must realize that kink-focused role-play with a focus on only smut writing will give this impression. Again, your persona will lead some to believe that you are indeed looking to use them as solely a sexual outlet.
When you combine several factors together, you will inevitably come across as undesirable to some.
Your singular and obsessive focus on pregnancy.
Your preference to only write with women.
Your preference to not write "non-erotic" role-play.
Your preference to write in the first person.
Now, you need to understand I am not maligning you here. The intent is not to chastise or criticize you. What I am trying to express to you is what has been touched upon in a few different ways already, but maybe not so directly. What you have is a perception problem. I am merely trying to spell it out in my own way to give you more feedback on why you are likely struggling to find partners. I have never interacted with you in private, so I have no idea how affable you are or what your intents are behind closed doors. I am giving you the benefit of the doubt, and assuming you are just very interested in writing one particular subject and prefer to write sexual material. These things are not against the rules. However, even when taken in the best light, it puts you in a position where your pool of potential partners is extremely limited, and those that might be interested might perceive you in a less than flattering light.
Bluemoon is a safe place to explore just about anything you'd want to explore within the confines of written role-play. However, it is a creative space full of people that have had many bad experiences with people that share many of the same surface traits you exude. Keep that in mind, and move forward with adjusted expectations.