I have had problems with my singing voice for months, what is wrong and how do I fix it?

Your 19 and still have about 18 months before you are out of puberty and then as your torso and lung muscles keep growing the voice will gradually settle down by the time your 27 or 28. It is obvious that you have probably been doing damage during the mutation change of your larynx. This is because your larynx, vocal muscles and vocal ligament have been lengthening, getting larger and wider which means you should be losing some of your high frequencies but gaining in lower frequencies. If you have been straining to keep your high notes then you will have been over tensing your vocal muscle and ligament which is why you may now have swelling within the larynx or worse still - vocal nodules. Any loss of voice means damage!! End of story!! This is why when we go to Sports days and we yell and scream we usually lose our voice. This is damage and is known as Laryngitis - which means swelling of the larynx. We lose the voice because the swelling stops the Vocal ligament from vibrating and vibration is what is called frequency or pitch. I would suspect you have swelling which can go down after a day and you will have your voice back, but the swelling only goes down a little so you should not sing for 5 to 7 days after your talking voice is back. I would suspect you also have the start of nodules and the turning of the head and voice cracking is proof of that. Go to your local doctor and get a referral to AN ENT specialist as soon as you can so that he can do a transnasal fiberoptic laryngoscopy {TPL} and if you have done damage he will send you to a Voice Therapist. Better still go to a really good voice coach [with the pictures they will take of your larynx] so that you can get help. One that is qualified in Laryngeal Biomechanics,ask them questions and see if they can give you the answers I just have, then you will know just how good they really are. But please, please get help before you lose the natural talent you have through lack of technique. By the way, herbal tea aint gonna help you. Better to get some Manuka Honey and drink this in a little hottish water. It is antibacterial and will get rid of any bacteria lurking in the mouth and throat. It is expensive as it comes from New Zealand but globally singers use Manuka Honey. Just don't drink too much as it fills up your bladder and your lungs can not expand to inhale or expellate air and every singer needs good airflow. I hope you haven't done to much damage and good luck.