You must be in your late 30s, I'm guessing, if you're thinking it's unlikely you'll 'have time' to have a family, now. There are more options than you think. The path doesn't have to be 'Get married, get a house, have 2.4 children, grow old together with pipe and slippers.' You don't have to attach your happiness to that idea. Do something different.
Also, sometimes it helps to recognise that everybody feels crap sometimes, and to have a little self indulgent wallow. It's self soothing, and quite nice on your birthday, to settle down on a comfy sofa with a box of chocolates and a bottle of red, put a big blanket over yourself, and watch 3 films in a row. In fact, many, many people with the husband and kids you wish you had would kill for the opportunity to do that. Indulge yourself in having a little cry, accepting that you're feeling shit, and giving yourself a supportive cuddle, some love, and some treats. Be your own shoulder to cry on. It's ok to feel shitty sometimes. Don't pressure yourself to feel differently; we can't control our feelings (the world would be a very different place if we could), they are our own personal wilderness. They are the part of us that stays 'nature'. Sometimes it's sunny, sometimes it rains, and all of it is ok. All we can do is respect and accept, and do things that help us feel nice, regardless of the emotional 'season'. The more things you do to make you feel nice, the sooner the season will change. Give yourself that gift for your birthday: 'This year, I'm going to do lovely things for myself.' 