UCCK I have this problem, too!! ~Here's what I do...~
The MOSQUITOS in Texas are HUGE. Not only that, but we have animal companions we share our home with [every-fur is invited :)] so we have many fleas, as well.
I, too, find my bites are big, red, itchy and swollen - and painful! We don't have screens on our windows, either - so I laid a cloth on the windowsill and dropped perhaps 10 drops of Citronella Essential Oil on there. Later, my roommate hung the cloth right above the windowsill - I don't get bothered by 'squitos anymore!
As for the fleas, I put a couple of drops of Tea Tree Oil into a shotglass with coconut oil and I rub that on my body. I plan on trying White Tiger's mix very very soon!
If you have pets at home, you can put a couple of drops of diluted Tea Tree Oil onto their collar or their neck area, where they CAN'T lick it.
Do you eat bananas? Mosquitos love banana eaters! They can sense the oil in your body and hone on in!