No pets, have been getting bitten for two months.

Hello,
This site has been extremely helpful. A lot of good tips and information. Thank you for this.
I have been looking over your site for about two weeks now and cannot seem to find answers to my unique situation, so here it comes.
I went on a cruise vacation in August. I was back home for a day when I noticed two mysterious insect bites on my lower leg. I didn’t think much of it until the day after next I had two more, again on my lower leg. I didn’t know what was biting me, when, or where, but I wasn’t taking any chances. My mind immediately went to bed bugs, so I buckled down to try to do whatever I could.  I already had a mattress and boxspring cover, so I washed the bedding on hot and dried for an hour on high. While that was going on, I vacuumed and steam cleaned the mattress and boxspring and also my upholstered furniture. I used a spray called Sterifab on my bed frame, the mattress, boxspring, and on furniture. I then used a long-acting spray Bedlam Plus in cracks and furniture joints. After a week with no bites, suddenly, I’m being bitten again, two at a time on my lower legs. I had a bed bug inspector come by, but we could find no trace of ANYTHING, anywhere. At my own request, even though there was no physical evidence of any bugs, I had them heat treat my apartment. The temperature was about 140 degrees F for about 5 hours or so. They also sprayed some sort of soy-based mixture all on the carpet and along baseboards and cracks. After a week of STILL getting bitten, the exterminator did a second soy-based spray for free. The bites stopped for seven days. I got one, single bite near my ankle yesterday.
I finally saw it though. I was saving my legs when I saw a small, spot on my foot. I assumed it was a piece of lint and brushed it off. The little thing jumped! It was so fast, that I thought I imagined it at first! It was too quick to really look at it, but I could not crush it with my fingers, and I soon turned on the sink and washed it down the drain. I went to wash my sheets, and found clearly a single dead full adult flea under my covers! Since it was dead, I got a good look. It was dark brown and glossy and appeared to have long hind legs, to me, all the distinctions of a flea. I have since seen another live flea, also during my morning ritual.
It is likely that I was so focused on the issue being bed bugs, that I overlooked fleas, as they are so very tiny and can easily look like lint or crumbs if you don’t know what you’re looking at. However, I do not have any pets. My boyfriend has a dog, but is up to date on his monthly flea treatments, and I have not found any fleas on the dog, nor has he ever scratched himself. My boyfriend has never been bitten, either. I live alone in an apartment. My upstairs neighbor has a cat, but they never let it out.
I do not know how I could have gotten fleas, but without a resident pet (my boyfriend’s dog never comes over), why am I still dealing with this two months later? In the past, I vacuumed 2 to 3 times per week when the bites started, but have recently been doing it every single day (this includes upholstered furniture as well as carpet). I have a Shark Rotator Pro Lift-Away vacuum with a great pet hair tool. I wash my bedding three times per week. I run my clothes through the dryer on high for an hour before getting dressed. I am at my wit’s end. Any recommendations on getting this to stop? A lot of your other responses to people without pets seem to point to the problem resolving itself in relatively short order, since human blood isn’t the best nutrition for them, but like I said, it’s going on two months now. An insect infestation is pretty much my worst nightmare. Thank you in advance!