If you workout at home, does your weight rack look like this? ^ Or close to it? If not, you may not be progressing like you could.
You won't lift heavier EVERY workout, but you should have enough weights at your disposal to do so when you need to. They can be pricey, so you have to save your pennies, but it will be worth every one.
If buying heavier weights isn't possible at the moment, then you should be doing MORE reps with what you do have; or incorporate drop sets more often. For instance, if your weights go up to 30#, and you can easily do 8 dumbbell bench presses with the 30's, then you HAVE to progress somehow. Either push out 10 reps next time, or do 8 reps with the 30's; drop them, and do 8 reps with your 25's (or however many you can eke out).
See what I'm getting at here? PROGRESS. You will only force your body to change, if you challenge it as often as possible. It will quickly adapt to what it finds "doable". You've got to make it say, "Oh, shit!!! I can't lift that. Oh, wait...maybe...OMG! I can lift that! It's a bitch, but I CAN!" You've got to FORCE it to change.
You know what you'll force it to do? GROW. It has no choice but to grow stronger; work harder to recover (metabolism, baby); and be ready for the next time you make it say "Oh, shit!!!"