Hi Andy,
I agree with the advice given by the guys above, but there are a few more things you may need to consider.
Diagnostically, you may have a presentation known as Osteitis Pubis - google it for more info - but it can be involved in "chronic groin strain" presentations. A CT may diagnose this. In this case, a comprehensive exercise program is your first option. If this fails to resolve you may consider "prolotherapy" which has shown to be effective in chronic adductor treatments. I talk about it a bit here Prolotherapy Or AND here RICE or MEAT Protocol for Acute Ligament Sprain Treatment | The Sports Physiotherapist.
With reference to your current exercise program, you seem to be concentrating on "stretching" the groin/adductor muscles. You may find greater benefit with the addition of some or all of these exercise to your program (check out YouTube for examples):
Groin Strengthening - e.g. Theraband Adduction in Standing
Gluteal Stretches (as tightness in the gluts will synergistically increase groin strain)
Core Stability Training
Femoral Nerve Tensioners
I really hope this helps. If you require clarification send me an email and I'll flick you some links to good youtube clips ([email protected]).
The Sports Physiotherapist