Firstly, you need to see your primary care doctor. They will be the best people to run some initial tests. They will most probably do some blood tests initially to exclude infections as the problem. They may then order a biopsy. Depending on the results of the tests then they will refer you onto either a hematologist or an oncologist. Either of these will be able to help treat it if it is lymphoma.
The symptoms of lymphoma are quite general though, so don't jump to conclusions just yet, They can be caused by a number of other problems too.
I hope everything comes back clear for you. All the very best