Congrats on the courage to push yourself and your trumpet playing. I'm making some assumptions (probably poor ones so apologies in advance if so) on your length of playing given your post about your playing knowledge. Proper form may help. This means, keeping your elbows out, stand (or sit) tall, shoulders back. Now the best tip I can offer, use your diaphragm. If you aren't sure how to do that. Place your hand on your stomach. Now breath in making your stomach expand first, then your lungs. This will roughly double the air you breathe in. More importantly, you'll be able to deliver the air more powerfully using the strength of your diaphragm. Practice breathing like this, hopefully it'll help.
Here's a guide I found on properly holding the trumpet or flugelhorn. Good luck with your playing !