Welcome and thanks for posting your query to HCM.
After reading your query it appears to be possibility of either a insect bite hypersensitivity
or a starting of a blistering disease. Now from the history only we can not predict the exact cause to your problem. As the blisters are regularly forming so very first thing to be done form your side is to check for any insects such as mosquito or bed bugs. If it is not there and still the blisters are forming then it is best to consult a dermatologist
as soon as the blister is formed.
Meanwhile do not pop up the blister form your side as it can get secondarily infected and then you may need antibiotics.
Hope it helps you.
With good health wishes.
Dr. Sanjay Kumar Kanodia