Lump after surgery

I has my second lumpectomy in November last year, this turned out to be just a cellular fibroadenoma, my previous surgery removed a phyllodes tumor. Since then i have developed quite a large lump just behind where i had my surgery. i dont want to overreact and think its something bad if this is just scar tissue, has anyone experinced this after surgery? should i go back to the doctors just to be safe? Thank you