Well, if I spend too much time responding I'm going to get on a soapbox. I am 45, so hugely proud of my lifts. I'm at 350 for deadlift, 365 for squats, and 265 for bench press. My goal is 400/400/300 respectively. If you say a picture of me 10 years ago you just would not believe I'm the same guy...
Let me start by saying there are a thousand philosophies so mine is just one of many.
dump the treadmill.
I think that might be the WORST thing you can do for your joints. If you want an aerobic workout, consider a nice rower like the Concept C2. Pricey, but way better for you. However, I read two great books that really changed my opinion on exercise. One is a book titled "Younger Next Year", which I think everyone in their 40s should read.
Part of the premise of the books is you should do cardio to increase the length of your life, and heavy strength training to increase the quality. When I travel and use a hotel gym, the heavy people are always on the bikes, treadmills, etc., while the truly fit people are using the free weights - that sold me.
I read a book on body building called Braun. It's not well written and can be a tough read, but it changed my life. I adopted the same attitude of a body builder, focusing on the big compound lifts (deadlift, squat, bench press) and augmenting with isolation exercises. I started with a 5 day a week, total body program using dumbbells. I remember when I first started at 40, I could barely do 10 sit ups. Now in a given week, I will do 3 days of 3 sets of 20 with a 25lb plate behind my head, one day with 3 sets of 20 using a 35lb plate, and 1 day of 4 sets of 25 unweighted sit-ups. A strong core makes everything in life better - including sex. I don't say this to brag - just to illustrate - YOU CAN DO IT but you have to start with what's manageable and keep moving forward.
I have logged EVERY SINGLE EXERCISE I've done for the last five years. I have a spreadsheet that has 4 week's worth of columns on it. I will fill it out as I workout. When it's full, I will make a new copy of the spreadsheet and adjust accordingly. For example, I might find that a certain workout is stressing my triceps, making the next day's exercise's difficult. so, I adjust and move things and change weights. If an exercise goes up in reps or weight, I highlight with a yellow highlighter so I can see the progress on the sheet. If an exercise was easy or I think I can push it further next time, I put a + next to the amount. You really can't remember a week later how things went for you, but the notes are right there. EVERY SINGLE DAY I work out I log it. I think this is absolutely critical.
It's a marathon, not a sprint. Think total body, log everything, and make sure you don't be lazy and only do exercises that you like. Do you know how many guys only work their upper body? It's crazy! Do you know the exercise that works more muscles in the human body than any other? It's the deadlift. When I started, I could not do 20 goblet squats with a single 20lb dumbbell. Five years later I'm doing 350 and I WILL hit 400 by fall. Squats work your biggest muscles and create some of the biggest boost of growth hormones. Do do deadlifts, you will need to work your grip, so you work your grip. Again, think TOTAL body. As you go, you will start realizing your weaknesses, so you spend a little more time the next month on those weaknesses, but keep the total body approach going.
I'd be happy to share my workout, but it would not be appropriate for you. I could share what I started with if you're interested... I can tell you that all of the miscellaneous aches and pains have all gone away (a foam roller is your friend), and while I'm happily married I can tell you that women (and men) engage me differently.
I thought the way I looked at felt was just the way it was - a fact of aging. I'm so glad I sorted out the hormones (well, we are always working on that), changed my eating, started working out - my life is so much better than it was 10 years ago and gets better every year.
Ooops - I think I warned you about the soap box.