So i was getting my guinea pig out and i set her on my lap so she can sit with me at my desk and i noticed that she has a lump on her belly. its kind of hard when I touch it and it is between her front and back legs on her right side. i am not sure how long it has been there but i don't think very long. she is 4 years old and i am so worried for her. i cant take her to the vet so i was wondering if any of you might know what it is?