I get sick a lot and my WBC in CBC were 7.5 the range is 4.3-10.0. So that's good. Why do I get sick still do much? Can lymphoma cause this?

Frequent infections. Frequent infections are can be related to alltergies, chronic infections, inflammatory conditions, chronic disease. If you doctor said everything looks okay on the lab work you may need to work on improving your diet, increase your vegetable and fruit intake to 7-9cupse per day, use anti oxidants and anti inflammatoires, add a probiotic and use a neti pot if you have allergies if worse, seek help.
WBC=7.5 is NORAMAL. If you are concerned about lymphoma, you should see you primary care physician right away.