instagram account hack?

[salis]

So I hashtag on my pics all the time, but today one specific hashtag stopped working...i've been using this specific set of hashtags for months, and all of a sudden if i post it on ANY of my pics, Instagram logs me out instantly and I get an email saying "We detected some suspicious activity that suggests your Instagram account may have been compromised. Don't worry, we've taken measures to secure your account. As a result, we need you to reset your password, using the links below." SO, i'm forced to change my password because when I try to log in, my password doesn't work. I thought it was a hack at first..but I don't think it is. It's just this specific set of hashtags that are doing this to my photo on only my account. My best friend tried teh same hashtag and nothing happened to her account. HELP
PS I've used this hashtag before....so why is it doing this TODAY?? i've had to change my password over 5 times today because of this.