Menstrual cup experiences?

I'm 19 and I started my period at 13. I'm at university now so damn broke and it's annoying me how expensive tampons and pads are :/ I use organic tampons because I don't like the idea of putting something with even traces of fertiliser inside me tbh and I use the silk range Always pads because every other type gives me a rash when I wear them so it's even more expensive for me. It also really annoys me how much waste there is with pads/tampons (environmental impact terms) and I've been looking for another option.

I've just got some questions about menstrual cups, they might sound stupid but please bear with me :P

-Is there any issue with keeping the blood inside that long? Because you can keep them in longer than tampons.

-How do you know which size to buy?! I'd go for a reusable one and they're not cheap (in student terms) so I don't want to mess up but I have no idea what size my vagina is to compare to other women.

-Do you have to wash the cup after every use? I have a shared bathroom at uni with 7 people mixed genders which is just a big room with two shower cubicles, two toilet cubicles and three sinks in the open. I don't have a sink in my room either. Point is, I don't have a sink next to the toilet so washing it would be a problem if I had to do it every time (I don't mind doing it at the end of the day because I'd switch to a pad). Also, if you don't wash it every time, how do you feel about putting it back in with blood? Idk if I'd feel weird about it or what?

-How easy are they to clean? Awkward sink situation, don't fancy hanging around with the possibility of a guy walking in.

-Do they hurt at all?

-Is it difficult to put in after starting your period?

-Could it get stuck?

-Are there ever any leaks? Do you have to wear a liner as backup? I do quite a bit of exercise and some flexibility stuff, don't fancy anything awkward happening...

-How much does it fill up?

...sorry if any of those were daft haha. LASTLY: What are your experiences? Would you recommend them? Which brand?

Thank you ?