I must IMPLORE you to see a doctor. I started having foot pain about a year ago.... Waited a while to see a doctor and it turned out to be plantar fasciitis from wearing bad shoes. Unfortunately it didn't end there, I did not have insurance so I didn't get appropriate care. I now have posterior tibial tendon dysfunction which means I will be wearing a bracing custom orthotic for the rest of my life. I am only 28, and to top it all off the tendon issue caused me to develop arthritis in my foot and ankle. My knee also hurts as well. I am not trying to scare you but you must see a doctor to rule out any medical issues. Being overweight stresses our feet more, along with incorrect footwear and you have a very big equation for pain/damage.
Things that you may want to try to hold you over are:
1. freeze a water bottle and roll your foot over it for 5 minutes each foot 3-5 times/day. (ice massage) You can also ice your ankles
2. stretch your feet by pulling your toes back toward your leg, very gently until you feel a slight stretch.
3. Do calf stretches (gastroc, soleus, etc)
4. But over the counter shoe inserts/orthotics-my Dr. told me to get Power Step or Spenco- I must mention this was not enough in my case.
5. Get a gait analysis at a shoe store to find out if your overpronate. You may also want to try some shoes with a rocker bottom which decreases stress on your feet.
6. Do ankle range of motion exercises and heel raises
7. Take Ibuprofen to decrease swelling and control pain (if you're able)
8. try wearing a figure 8 ankle brace if you feel like you need the support
But MOST importantly get to the doctor. Everything I listed above are things I was told to do to improve my condition in the early stages and now forever. I hope it turns out to be nothing serious

I know that list looks crazy but I wish someone had told me that stuff before I developed more serious issues. Good luck!