I agree with SilverSage, you will hear of people with a TON of experience with one particular species being able to "guess" the gender of that species...But even with someone who has years of experience with a specific species, even they are still just guessing...So the DNA-test is a must if you want to know now, which is a very good idea so that you'll know whether Eggs are going to be a possibility in your bird's future, because with infertile egg-laying can also come Egg-Binding, which is extremely serious and require immediately medical attention...
***Just a word to you for the future, as I think it's very important...I understand not wanting anyone to "stick a needle in your bird", but this is EXACTLY WHY you need to find a very experienced Certified Avian Vet or Avian Specialist Vet NOW, BEFORE your bird becomes sick or is injured, so that if/when that happens to your bird in the future, you can feel confident and comfortable that they know exactly what they are doing when it comes to medical procedures...And a simple Blood-Draw from the neck of a bird is something that ANY Avian Vet who is worth that title can do in about 30 seconds, without any sedation or anesthesia, and with no problem at all! I've done it hundreds of times and I'm not even a Veterinarian, but I've been thoroughly trained, and it's 100% safe and easy...My first blood-draw on a bird was to a Turkey, believe it or not, lol...
***The other reason you need to find a CAV is because all pet birds/parrots should have a full Wellness-Exam at least once every single year of their lives, and these yearly Wellness-Exams need to include full Fecal testing and full, routine, baseline Blood-Work, which means a blood-draw from the neck. This is the ONLY WAY to stay ahead of any illnesses your Alex may be hiding from you, as well as monitoring the health of their Liver and Kidneys, and also gauging how their daily diet is treating them nutritionally so you can make the necessary changes. And you want baseline Blood-Work results from when your Alex was healthy to compare to if he ever becomes ill.
Trust me, the way that all birds hide any and all outward signs of illness and pain for as long as they possibly can, typically it's at least a month or longer (sometimes months and months, depending on the illness), the ONLY WAY to catch illnesses, infections, Avian Viral Diseases that can be fatal without treatment, etc. is to have routine Blood-Work, a full Fecal, and a full Wellness-Exam (visual and physical) at least once a year. Trust me, the 30 seconds it takes to draw blood from your bird, which is 100% safe if done by an experienced Avian Vet, is a lot better than losing your bird to an illness or disease that is easily treatable and curable if it's caught early enough to treat...