Not interested in sex

So I have been dealing with this for about a year now I have had little to no interest in having sex with my man. I don't know why? I mean obviously I have to please my man but I will go weeks and he gets mad. Does anyone else feel like this or ever felt like this I'm only 23 I feel like I should want it all the time I use to? I just don't know what happened!! Any answers or help would be greatly appreciated!!!