friends can't join my server?

[Paige.]

i made a new server the other day (no hamachi, i port forwarded and used www.no-ip.com) and once i had made it, everything was fine and my friends were able to join. the next day none of my friends were able to join, 'can't reach server' and it was fine for me and i could join and everything? my brother tried and he could join but none of my friends could..
i've tried everything i can think of and i've searched everywhere like google and youtube and i've:
deleted the whole thing and re made it twice from scratch
tried port forwarding again about 4 times
i allowed minecraft server through windows firewall
i tried using different ip address's to give to my friends like my ipv4 and i went on websites to find my ip and gave them that
i tried loads of different settings on the property file
and loads of stuff but nothing works

is it just that my internet is bad or something? i don't know why that'd be because i'm with bt and i have super fast internet so i don't get it

i'd appreciate any suggests or help, thanks

[Paige.]

fixed it woooo!!