As others have said, get your bike fit sorted first, and then work on upping your distance. 30 miles is my daily round trip commute to work. When I started commuting to work by bike 3 and a bit years ago, I only lived 6 miles from work. That first day, I thought I was going to die half way in. By the end of the first week, I was making it to work without stopping. By the end of the second week, I could make it all the way up the hill into work and my time was starting to get faster. I then moved a bit further away from work (15 miles), so I went for a couple of longer rides, and made sure I was comfortable, then started commuting 2-3 days/week. Soon after I got a road bike, and joined a club. I was a bit worried about whether or not I would make a 40 mile ride, I did. Within 2 months of getting a road bike, I rode my first metric century, in less than a year my first imperial century. Last year I did 150, and I just completed my first double century over the weekend. And 150 miles in, everything hurt. But I didn't get there without work. If you're struggling past 30 miles and it isn't a bike fit issue, maybe you're going too fast out of the gate. Slow your pace down. Ride with others to push yourself further. While training for my double century, I did hard efforts on my commute into work, pushed myself by going out with faster groups on club runs, and did a couple of long rides a month on top of that. My final build up ride for my double was only 120 miles in the end, but it had nearly 10,000 feet of climbing (which was more than the climbing on the double). Distance doesn't just come, you have to put in the work to get there.