Anxiety.. A mental illness ?

Laura
I have minor anxiety every now and then but the other day my boyfriend and I got into a huge fight about it because I was trying to help him understand ways to reassure me when I start feeling anxious. 
He got super angry about it all and proceed to say I'm mentally ill and should just seek out a doctors help.. Which obviously made me feel horrible !. What do you guys think ? 
Would you consider anxiety a mental illness ?