Are these the same bumps you were talking about couple of days ago?
It definitely doesn't seem like allergies, especially seasonal allergies - those usually come in the form of sneezing, coughing, runny nose, stuffy nose, etc.
When was the last time you wore you new flip flops? I don't think its from flip flops because the distribution is in places where the rubber doesn't touch the foot (from what it seems on the picture). Also, if the last time you wore your flip flops was 2 weeks ago, you should be getting these spots now. If you were allergic to a product within that rubber, the spots would show up within 24 hours.
It is very possible that these are bug bites. But bites come in groups around the same area. The reason they itch so bad is because your body develops an allergic response to the bite.
I would suggest that you put Hydrocortisone cream 1% on the itchy spots (if you have another topical steroid cream that is stronger than Cortisone, tell me and I will tell you if its ok to use) and also take Benadryl before you go to bed. If you are worried that Benadryl will make you too sleepy, take over-the-counter Claritin 10 mg. Its the same thing as Benadryl but non-drowsy. Of course, change all your sheets.