My mother is very attached to one of our cats, but there is a weird bump on their head. We aren't exactly wealthy enough to bring it to a doctor unless it is serious or causes pain. The lump seems to be filled with fluid and sometimes disappears for months. The problem is that it usually comes back. It doesn't look like it causes our cat pain but it just worries me. She is getting old at around 14-15 years old. If it matters she has changed her behaviour recently and loves going outside, and craves attention more. about a year ago she lost a lot of weight and she seems very happy. Pictures attached