You should avoid dating for q while until you've learned how to spot red flags. Because this guy was a giant walking red flag.
Someone telling you they love you after 4 days - is a nutter. It's called 'love bombing'. It's something abusive men do in order to get you to let your guard down with them and trust them.
Read up on how to spot love bombers. Read up on how to spot players and abusers. Note that they often blow hot and cold. Acting really into you qnd then pulling away and when you need reassurance as a result of that, they make out YOU are the needy one.
This man is not a good'un.
Why on earth were you snogging a guy in uni toilets anyway? I'm guessing that wasn't your idea right? People who push your boundaries are not good to be around.
What do you do? Block his number.
And you listen to your own advice- people who have known you 4 days not in love.
Also, be aware of other things that you noticed. Like fear of pursuing that topic incase he got upset. So he basically was already training you to not say what you feel needs said incase he reqdlcted badly (eg: huffs/guilt tripping ect... none of which exist in a healthy relationship).
I'd examine your own boundaries. We set boundaries for OURSELVES about about treatment accept from others. So when he was Rushing you with the L word, rather than having to explain to him why that's not ok at 4 days in, you should have left him right then qnd there. Why? Because no normal person needs to be told its not ok to tell someone you barely know that you love them.
If you find yourself explaining why shit/pushy/unacceptable behaviour is shit, pushy or unacceptable, you are potentially in, or on the way to being in an abusive relationship.
I think you've had a lucky escape.