Soft fluid sack under skin on shaft of Penis

My question is concerning an almost quarter sized sack of fluid on the bottom/ventral side of my penis running atop of the urethra and a little below the head. As I said it's about the size of a nickel and visually noticeable from any angle erect or flaccid, however there is no discoloration to the area of the skin. It feel like a squishy sack of fluid that can be moved around or *almost* flipped upside-down, however it will always return back to the same spot (this makes me pretty certain that it's connected to the skin and not the actual shaft of the penis). There is no pain, and I have had this for a while about 6-7 months now, however I have not been as alarmed about it since I have been getting these for the past 5 years on and off with it dissipating off on it's own, however each time it does come back it seems to last longer and become larger (this is probably the 3rd time I've had in over the course of 2 years). I would consider popping it, but because it is underneath the layer of skin with all of the blood vessels It seems a little too risky of a thing to do. Other descriptors: -When my Penis is flaccid it can be pulled away with the skin from the penis body -if some light source is applied to it specifically light will glow through (i.e. not really an opaque fluid)-Lately (months) it hasn't changed size at all regardless of erection or frequency of sex (not even afterwards)-No pain at all under mild to moderate pressure (or even during sex) -Almost feels like a water balloon. -If I do masturbate it's hardly rigorous at all, but doesn't respond to decreased frequency  I'm just trying to make sure that this doesn't seem to be some dangerous growth that needs to be properly removed or if there's some way I can shrink it into submission (due to it's embarrassing location) I have had sex before, but the first time I got this lump I had not. Thank you in advance for any information you can provide, Dalton