Your pumpkin's specie is either Pepo or Maxima. If it is Pepo, you could cross pollinate with any of the summer squashes, Acorns, or Delicatas. If it's a maxima, you could cross pollinate with Hubbards, Kuris, Bananas, and the like. It could have happened already by bee activity if there are other squashes around. Maybe you know someone with a garden and a suitable squash with a male flower that they could spare. All you need is the correct species. Get the male flower, strip the petals, and dab the dusty inner stamen onto the insides of your pumpkin's female flower. Yes, this means the male flower is decapitated and killed in the process.
Check the seed package to identify your pumpkin's species, or Google the variety if that doesn't work.

My pumpkins bloomed male/female flowers for quite some time. Not all will become pumpkins. It's still really early in the season; I'd give it time to bloom more.

In gardening, you just have to come to terms with the fact that not every single flower will produce a fruit. We do love our plants, & we do our best, but you will never get to eat 100% of what you plant. One flower is not a crisis. Plant a few more than you think you will need, to allow for possible loss, & for better chances of pollination. I used to practically cry over any plant loss. I still can't bring myself to "thin out seedlings" but I think the tool you most need is patience. There will be more flowers. Just love them & nurture them & let them produce when they are ready.

I don't know if it will work for you or not, but there were no usable male flowers open when my last female flower opened. I took one of the closed male flowers that were starting to "ripen" and getting ready to open and peeled the flower petals off of it. I rubbed it with my finger to be safe and some pollen came off even though it was not yet open. The best thing I can say to do if you're worried about it, is to just test it. Worse comes to worse you cut a male flower for nothing. Oh well, there will be more later. Or, if you don't want to do that, you can wait. Everyone else is right, there will be plenty of male and female flowers later. My watermelon plant did that. My female flowers opened first and started dying off. I know, it's odd and I couldn't figure out why. Anyways, the male flowers came a bit after that and I had lots of personal sized watermelon. Good luck to you and keep up hope!