Everyone does understand that; what your family needs to understand is that is the downside of the only child issue and that's completely out of your control.
Let's play a little bit of "what if?", and please understand that this is only a scenario. Let's just say you did find someone, have a whirlwind courtship and romance, then get immediately married. Then what if you find out down the road that someone was unable to reproduce (either you or him). What then, will your mother still be upset? You got married just like she wanted you to, but now you still can't give her what she wants. What do you do now?
Marriage doesn't guarantee children, hence the number of infertile and childless married couples around the world. Now the next time your mother comes at you with the "when are you going to settle down, get married, and give me grandchildren" questions, give her the scenario I gave you and see what happens next.
And no one here can tell your mother anything, you're a woman in your thirties and capable to to tell her yourself. Since you don't live with her, you don't have to leave yourself open to the conversation if you don't want to. When she starts in on the stuff you don't like to discuss, tell her "wow, look at the time, I really have to go!" "Love you mom, talk to you later!"
As far as love is concerned, I subscribe to the theory that you don't look for love, love finds you. You have to be ready to receive it when it comes so take care of any internal issues you may have so you leave as much relationship baggage behind as possible. We all come with some baggage, but keep it to a minimum whenever you can.
You can either settle for just anyone or you can wait for the right one, the choice is yours.