Hello, I'm going to start this post out with an overview of training injuries and lower back pain, so it may end up being a bit lengthy. So I want to thank you for your input and help now

Been lifting since 2009-2010 (freshmen yr highschool), I began developing back pain around the beginning of 2011. I attribute this mainly to doing heavy box squats on a smith machine (very stupid). 2012 I did not train legs at all after deciding to not play football or sports my senior year. After graduating in June 2013 I began training legs again just for balanced physique/aesthetic purposes (my "bro" phase had ended).

In Sept of 2013 I injured my lower back squatting 185 while still warming up. On my way down I did not stay tight and at the bottom I felt a weird pain (like icy hot kind of) in my lower back. For the 3-7 days following I could not even walk properly. In total I was out of the gym for just under 2 months. After returning my lower training took a few different turns, but never really addressed my weaknesses as I should have. Began low bar squatting.

Recently, in October 2017 a similar thing happened again when squatting, it did not affect my ability to walk like the 2013 injury. But I was out of the gym again for another 2 months. I recently began training full throttle again and addressing a lot of my issues/imbalances (core strength, squat form, etc.).

Now I cannot seem to squat or deadlift comfortably. I can't find my groove in either and they both feel very uncomfortable on my lower back. I do not want to give these movements up, though. Recently I have discovered when walking if I extend my left leg a little beyond my average stroke length I get a pain above my butt on my lower left back, which I believe is a sciatic nerve. This is also bothered when deadlifting and squatting.

I am going to see a PT, but it will be almost 2 months until I can get in. What I'm asking for is:
1. Help from others who've been in the position
2. I need to improve my mobility/flexibility drastically also as I feel stiff, advice on a mobility routine
3. Should I cut out squats/deads?
4. A program for strengthening my core and lower back

I've spent sometime on Joe DeFranco's YouTube channel... While he has had much more serious back injuries he said he has discontinued the squat and deadlift, and moved away from crunch based core movement (his leg training is based around unilateral movements that avoid spinal compression/allow you to remain upright.. like lunges, sleds, step ups, etc.), as well as core training that is among an anti-movement pattern (mainly planks, etc.)

I'm leaning toward going Joe's route until I see a PT, but would also like feedback as I'm sure many of the fine men here on AM have been there, done that in regards to my position or similar. I was also going to begin doing his Agile 11. Should I do this daily, and should I add more mobility work on top of this?

Thanks y'all, all feedback in appreciated!