hi guys,

i am new to running, beside ruining for my 4km and 1500m during my school time (which is 20 years ago, now 35 years old)
Currently am training (no previous race experience) for half marathon (SCKLM) that held on this April 2018 for almost 4 weeks

been doing 2 run a week
one short 3km run during weekday and one long run during weekend (best performance is 12km)
for long run, i am doing run walk. i will walk for 1~2min every 2km.

I also been lifting weight 2~3 time a week but since i introduce my running training in to my schedule
i have recovery problem specially after the long run or after my heavy lifting week

below is my new program schedule:
wakeup at 6am, start 6:30am and complete workout at 7:30am and go work at 8am
I reach home at 8pm and i need to take care of my baby, therefore no workout after work

Mon - Rest
Tue - Weight (compound movement - pushup and deadlift)
Wed - Weight (compound movement - push and pull)
Thu - Run (3km)
Fri - Weight (Squat & accessories)
Sat - Rest
Sun - Long Run (Aiming 10km and about)

the problem happen last Sunday, when i fail my long run at 4.5km and feel like my body is breaking apart.
Previously i been doing 8km (1st week), 10km (2nd week) & 12km (3rd week)
my body have so much pain from neck to my lower back after the 4.5km run and i still can feel the pain today at my lower back.

i suspect is my heavy squat on last Friday

my question, is this the sign of over training or just a phase that i need to go through to get my body adapt to this new schedule. 
Thanks for reading and hopefully sifu here can give some advise