Has anyone ever experienced horrible lower back pain on clomid? Any clue what this could be...hopefully not overstimulation! I'm on 100mg, FYI

Thanks ladies! I know if anyone will know, it's you guys!
DH & I married 12/17/2012
Me (31)-dx w/PCOS 2007, when married to ex-husband after MC
DH (41)-no MFI
07/2014-Femara 5mg + trigger + IUI= chem preg ;(
08/2014-Femara 5mg + trigger + IUI + 2nd trigger= BFN
09/2014-Clomid 100mg + trigger + IUI + 2nd trigger= BFN
10/2014-benched due to RE out of town, tying naturally!
11/2014-benched due to cyst
12/2014-Femara 5mg + stair step with additional 5 days Femara 5mg + trigger + IUI=BFN
01/2015-Femara 5mg + Gonal F 25 units + trigger (plus additional Gonal F 100 units on trigger night) + IUI= BFP!!! Twins due 10/2015
09/28/2015- Surprise! Conrad and Hudson born at 35w6d!
Re: Backache on Clomid
Natural Cycle IUI #1 : BFN, December 2013
BTW-love the screen name! I'm mildly obsessed with tacos
09/28/2015- Surprise! Conrad and Hudson born at 35w6d!