Starting about 2 weeks ago, I have been swimming 2-3 days a week, Running 2-3 days a week, and riding my bike 3 days a week. I am not starting this completely "off the couch" as I have been staying fairly active with a bit of running/swimming/hiking/very little riding for the last several years, just not consistently. With my swimming, I feel like I am over the hump where I can pretty much just keep swimming as long as I am not trying to swim fast. I am hoping there is a "hump" like this with riding that I would like to get to.

My rides the last 2 weeks have been for about an hour riding rolling terrain at probably 15-18 mph. (not really sure b/c I don't have a bike computer). When I finish each time, I definitely feel like I got a good workout, but not like I am over doing it.

I would like to build up to being able to consistently and comfortably ride 25 miles at a descent pace twice a week and comfortably do a 50 mile ride on the weekend. Maybe shoot for this goal by the end of October?

Just hoping someone could suggest a rough riding schedule for me. Is 3 days a week enough? or should I be riding 4? More than 4 is not really practical with my schedule. What kind of mileage/or time would you recommend. I want to make sure I am riding enough to improve, but don't want to risk any overuse, chronic fatigue, type of symptoms. I will also like to continue with running/swimming at least twice a week.

Hopefully you can provide some input. Thanks for your time.

Sounds like triathlon training? Even if its not, I bet they'd have training plans or advice for incorporating all three activities.
https://www.bikeforums.net/triathlon/

Get a bike computer (check out the cateye strada cadence, ~$35-40?), then figure out what you want for a decent pace. Riding 3 times a week for 1-1.5 hours, it won't take you long to build up to 25 miles if you can already handle 15-18mph. Just be sure to include days for rest/recovery (harder to do if you're going to push yourself on the running/swimming as well as the cycling).

Training by feel can be effective, but some objective measurement can help you maximize your progress. For example, you'll have to push yourself at times to get gains in cardiovascular capacity (like interval training). I think a pulse rate monitor, such as a Garmon forerunner 50 that you can get on Ebay for about $65, will enable you to train below your anaerobic threshold but still not slack.

Having said that, you are getting a workout nearly every day, and may not be planning enough rest days. Also it's important to eat properly and to get plenty of sleep for maximizing your training. Are you planning to do any triathlons at some point?

Running is a special case since it is more impacting on the knees and other joints. Hopefully you have eased into your running program with alternating walk / run periods and aren't overdoing it. It sounds like you have a good cardio basis already built up. Good luck.

sounds like your training like me, for triathlons. I am finding that this kind of training is really a total body workout. i have been at it 7 months now. not sure what your distances are in swim and run but mine are 3000 meter swim 3x a week, run 3 to 5 miles 3 times a week, biking is around 20 to 30 miles

My original plan was to do an olympic distance tri in september just for motivation to build some fitness. My reason for posting on this board is because as I have been riding (along with some running and swimming), I am thinking about shifting my focus to the bike (using swim and run as cross training).

I would love to get in some really good cycling shape, but need a rough guide to get there. Thanks for your time.

*I just purchased Thomas Chapple's Base Building for Cyclists. It may actually be more technical than what I am looking for, but it seems like a potentially valuable resource.