Getting back to my old pace after "injury"

I was doing 40+ miles 5 days a week before my "injury". I stopped riding for
about 3 months. Now, I have lost a lot of strength and ability. I know it
all comes back , but I worked really hard to get to where I was. I was very
commited to riding ,but I also lived 20 + miles from work. That is why I
could do that many miles. It was hard to find time. I would make myself do
it and use the bike as transportation at the same time.Now I moved (after
getting seperated) and live only 5 miles from work and my schedule has
changed . I want to get back to where I was physically. I started back on
the trainer a few weeeks ago and felt like I was starting all over again.
The past few days though, I feel it coming back. I started doing 10 miles/
0-35 minutes on the trainer 5 days a week. I will soon raise it to 15 miles
, then back to 20 which took me just over an hour. I am going at about 90
rpm cadence. I wanted to get into racing last year , but my injury sent me
backwards. I was told to do 85-90 rpms and 75-80 for climbing. I have never
rode in a pack before. I ride a trek madone that I got for a SCREAMING deal
off Ebay. and use a Giant OCR on the trainer. My injury is near the groin
area. It is half way between my belly button and testicles on my left side.
It feels like a bruise if you touch it and put slight pressure on it. It
hurt me so bad a couple months ago, that I couldn't work and had to stay in
bed. I was on vicodin. I had MRIs , Xrays, etc., saw 5 different doctors and
not one knows for sure what it is. I thought it was a seat adjustment
problem. At first , my primary told me it was tissue damage, then later he
told me it is stress related because of everything going on in my life. It
is still there today , but not to where I cant do cycling. Sometimes it gets
to where I'll pop 4 or 5 ibuprofen and it goes away. Anyone had anything
like this before? How should I go about getting back into a rythm? thanks