I've known three children who were dx'd with leukemia. all three kids' blood work were definitive that something was wrong. two of three presented with with not being able to get over an illness in a timely matter.
IMO, your anxious thinking is driving your fears and not lymphoma or leukemia. I have a concern that your anxious thinking is already trying to find reason to negate any blood work that is going to be done.
I am a H-U-G-E preacher of NOT googling symptoms or diseases, whether you are currently afraid of a particular disease or not. Googling just plants those little seeds. those seeds will take root at some point. Additionally googling stuff never assures a person they are well. Oh one may get a piece of assurance but with the HA mind, that won't be good enough and further research ensues and all hell breaks loose 9 times out of 10. If you continue posting here, you will see posts all of the time saying things like "I googled. Please talk me down" SO looking up diseases should be OFF of your to do list. .
A few other things that should be off of your to do list are: No monitoring of bodily goings on, self-check/self-test, seeking repeat reassurance from family/friends/internet/doctors. AVOID "peace of mind" medical tests. Certainly there are legitimate reasons to have medical tests and, thus, should be done. However, around here, more often than not, med tests are done just reassurance or "peace of mind". this sort of testing does not work. You will see many, many people advocate such testing and you will see many folks having them. Unfortunately, such tests accomplishes either: 1. person doubts test--it was done too early, it wasn't THE right test, or doc read it wrong, 2. person accepts the test but soon thereafter or down the road a piece anew crop of symptoms, NOT covered by the previous tests, appear and the person is a mess all over again. Basically these are "reactive" behaviors. Reactive behaviors only keep a mind/body amped up. It keeps us in the vicious anxiety loop. The fight/flight just diminish when it isn't constantly fed panic.