M1994, I want to suggest something for you to bear in mind that may be difficult. As you say, you have no letter from Hashem promising that you will eventually get married. I think you should consider, not in the front of your mind but just as a remote possibility in the back of your mind, that maybe, just maybe, Hashem has plans for you that don’t involve getting married.
YOU want to be a wife and mom, and for most women that is also what Hashem wants for them, but in some cases He doesn’t, and it is possible — not likely but still possible — that you may be one of the exceptions. Don’t expect that, don’t just give up on shiduchim and say “Fine, Hashem, I won’t get married”. Keep doing everything you’re doing and hope that He will help you, but bear in mind Abraham Lincoln’s wise words: “Let us not pray that G-d is on our side but that we are on His”.
IF and only IF it turns out that He doesn’t want you to get married, you should be prepared to accept it, not reluctantly as a sacrifice you give to His will, but joyfully as a gift that He is giving you, because He knows that in your case marriage would not be good for you.
Because of course you know that some people get married thinking this is what their lives are for, and it turns out to be a big mistake. People make themselves miserable by marrying the wrong person, or by marrying at al when they shouldn’t have. And some people are very happy being single.
So if that turns out to be your lot, be willing not just to endure it but to enjoy it and celebrate it and thank Hashem for it (while never losing hope that in the end His plans for you will include a good and happy marriage after all).
Just something for you to consider. Keep davening, keep doing mitzvos, and keep hoping, and very soon may you be Eim Habonim Smeicho.