Don't beat up on yourself. You may not have "blown" the interview. It might have nothing to do with you. I once spent near a year job hunting, it was a long time ago but I have not forgotten what it was like. Summer is coming, I don't know your interests but there are quite a few seasonal jobs (at summer camps, campgrounds, town recreation departments, stores in tourist areas, restaurants etc. and that can be a way in). Also, look at your applications, make sure they are clear, easy to read, concise---if you suspect a particular employer of poor review, leave them out (if asked about the time off there, make it a voluntary, active reason----this actually turned out to be my problem once---
also don't be afraid to walk into places to ask about work (an old time method but sometimes worth it) or to try something you hadn't thought of (I once got a job with a large company that I'd no knowledge of...just followed "employment office" signs)--
Now I am retiring and I keep getting calls with job offers so...do hang in there. Consider, if you are able, getting some training (eg: certification---check on jobs that just require certificates -- EMT, others...)