Frustrations with running

I've been pretty frustrated with running recently and I'm going to take a moment to be negative and write about it here since it's what I'm dealing with at the moment.

I started running in 2014, was always slow but saw improvements in my speed through 2016. My first half marathon was 2:57 and my half marathon PR in December of 2016 was 2:50 (about 13 minutes per mile average). I also had a 5k and 10k PR in 2016 so it was a good running year.

My 10k PR in March of 2016

But since then, I've just been getting progressively slower and slower and I'm not sure why. I didn't train consistently in the beginning of 2016 but starting in June 2016, I upped my running from 3 times per week to 4 times per week. I do speed work and I run hills. I strength train. And I still just keep getting slower. I started training for my first marathon (WDW 2018) and training went fairly well. Got in my 20 miler and everything. But I was swept a bit past mile 20 since I was behind pace due to knee problems. My half marathons last year were 3:10 and 3:19, a pretty drastic difference from the year before.

I had some tendinitis at the beginning of this year after the marathon so I haven't run for 4 weeks. I tried again this past weekend, just 2 miles, and it was an average of 17:30 per mile. Plus my heart rate was high. 40% was in zone 4. I can walk faster than that! I don't understand why I can feel like I'm working so hard but barely moving forward. It makes me wonder if there's something physically going wrong that I'm unaware of. I do have thyroid problems but I've been on medication for that for a long time and those numbers are normal on my blood tests. My most recent blood test did show high cholesterol and low vitamin D. I have started taking a Vitamin D supplement.

At least the Spring flowers provided beautiful scenery on my run

I guess I'm partly venting and partly looking for any tips. Can anyone think of other reasons that people may have a drastic slow down like this? I did turn 40 last year and I had gained some weight (7 pounds since my half marathon PR). So back to being positive, here are some things I am going to do.

1. I am working on losing weight, mainly for the purpose of getting my cholesterol down but hopefully that will help with running as well.

2. I guess I should re-evaluate my running form since clearly, the effort I'm putting in is going somewhere but it doesn't sound like it's going forward.

3.  I'm going to ask the doctor for a full blood analysis.  Someone mentioned iron, and it has been a while since I've had that checked.  I've also considered it may be peri-menopause or something hormonal like that.

4.  Be patient with myself.  I know this is my first run in 4 weeks after being in an ankle brace and no activity so I need to be patient.  Hopefully as I get some more runs under my belt the pace will naturally increase back to where it was last year before the marathon, and then I can work on speed after that.

It's just frustrating to feel like I'm working hard and doing the right things but continuing to get slower, to the point where I can walk faster. And if I can walk faster, what's the point in running?  I've always felt that as I got older, there would come a time when I switched to walking and that's fine because I would still be able to get the main things I love out of running with walking.  But I just didn't think that time would be so soon.  Hopefully it isn't that time yet and I can figure out what's going on with my continued slow down.