Hi there dq15, sorry to hear that this is something that you are finding stressful at the moment. It is something that a lot of people with penises worry about; a lot of the messages that advertising and "society" say about what it means to be a "man" are exaggerated and unrealistic, and therefore cause a lot of stress to people that isn't useful, and well, stressful! Really, it sounds like you are on a pretty typical timeline at the moment, and definitely not "running out of time". Not only is 18 still quite a ways away (over 2 and a half years), most people with penises like yourself are done with puberty by the time they're 20 - 25, so 18 is not even usually when puberty finishes up.
To quote from the article,
Shown Actual Size: A Penis Shape & Size Lowdown, we have on the main Scarleteen site:
We are often asked what the average penis size is for, say, a 15-year-old. The trouble is that where someone is at in puberty isn't the same for people of the same age. For most, penis growth starts anywhere between the ages of 11 and 16, and on average, around 13 or 14 years of age. Before penis growth starts, you'll usually have both a growth spurt in terms of your height, as well as testicle growth. Penises also will tend to grow faster or earlier in length than they will with width.
During the time that young people are going through puberty, before growth is completed, the average penis size for an adolescent of any age varies from between two to five inches. No one asking any of these questions is weird or abnormal: you're all just fine.
Penis growth doesn't happen overnight: it's gradual, just like any other kind of body growth, and may also happen in spurts. In other words, you may have times of some growth, then a long pause, then some more growth again later. By the time you're done with puberty, your penis will be done growing. People with penises will usually be done with puberty by the time they're 20 - 25, and when you're done with it can vary, and is influenced by when you started. Overall, someone who starts puberty on the earlier side will usually be done on the earlier side, while someone who started puberty later will usually end it later.
I understand that hearing this on the one hand can be comforting in the way it provides an understanding that you don't have anything to worry about in the longer term, but that it can still be a frustrating waiting for puberty to keep doing its thing when you've been stressed about it. Do you think about this a lot? Do you have any good ways you like to deal with thoughts or feelings that are stressful, or is it more like they won't go away? If you'd like some more techniques that can help you handle those, let us know and we can provide some pointers.