lumpectomy, rads and swelling

I had stage 1 breast cancer (ER+/PR+/HER 2 Neg), lumpectomy, chemo and rads.  I completed rads in June and Lupron/Tamoxifen were started in May.   In the last month, I have noticed swelling on the lumpectomy side and the tissue seems thicker.  Is this normal after rads because I thought the opposite would occur?  I had 5 lymph nodes removed (all negative).  Could it be a problem with lymphatic drainage?    What changes can I expect due to treatment?

Thank-you so much for your insight!!!  

PS- I just recently (past three weeks) had a breast MRI (Negative) too due to a false alarm in the contralateral breast (fibrocystic breasts).  

[Cleveland Clinic]

Dear duff0015:  Radiation therapy can often cause some scarring of tissue which could feel thicker.  However, without evaluation, we cannot speculate.  We recommend that you bring this to the attention of your doctor or radiation therapist for evaluation.

[duff0015]

I just wanted to add...

No signs of infection (redness, warmth, fever, etc).  The lumpectomy side is just slightly larger than the other side now, heavier, and feels thicker.  No palpable lumps.  Actually, the incision area seems a little softer (still granular though).   I'm on Lupron so no menstrual cycles.  Thanks.