Sounds like you have normal onions. What is happening is that onions are biennial and the first year they make a bulb to store energy and the second year all their efforts are put into making that large seed head and lots of seed. Since your onions spent the winter in the ground, they think it's the second year so they're making flowers and going to seed. Your onions won't really create big bulbs this year so you can either harvest them as soon as you see the stalks or let them go fully to flower and seed and collect the seed for next year's crop.

For zones in Massachusetts, you'd normally start seed inside in early February and set out plants into the ground in early to mid April. Once they're in, you'd be looking at a harvest for onions in the middle to end of July.

Makalu, thanks.