Losing pressure from combi boiler

[noobiediyer]

I've got a combi boiler which has been working fine. A few weeks ago, I noticed that there was a small puddle of water underneath the boiler. We use that space to store various bathroom products so wasn't sure if the boiler was leaking or if one of the bathroom bottles. Anyway, I mopped it up, cleared the area and monitored it for a few days. The water didn't come back so I assumed it wasn't the boiler. A few days after noticing the leak, I then noticed the pressure in boiler was really low. Thinking this was completely unrelated to the water leakage, I topped up the water level in the boiler which brought the pressure back up.

All seemed ok until yesterday (a few weeks after the initial leak). I noticed that there was another small puddle under the boiler. The boiler had a few drops of water hanging on it's underside and also noticed the pressure had also dropped. At this point I realised that the pressure was dropping because water was leaking from the boiler from somewhere onto the floor.

I have limited knowledge about combi boilers so hoping someone could explain in laymen terms. Why would the combi boiler be losing pressure and dumping water out? Is this is a serious problem or can it be fixed by something trivial? I don't want to call a plumber out if it's a simple remedy/maintenance task that is normal for a home owner to deal with (e.g. bleeding radiators or unblocking kitchen sinks etc).

Any help will be greatly appreciated. TIA